The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A115907 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A115907

Numbers k such that sigma(k) plus the k-th prime is a triangular number.
(history; published version)

#21 by OEIS Server at Fri Nov 09 22:10:43 EST 2018

LINKS

David A. Corneth, <a href="/A115907/b115907_1.txt">Table of n, a(n) for n = 1..11241</a> (first 1000 from Robert Israel)

#20 by N. J. A. Sloane at Fri Nov 09 22:10:43 EST 2018

STATUS

proposed

approved

Discussion

Fri Nov 09

22:10

OEIS Server: Installed new b-file as b115907.txt.  Old b-file is now b115907_1.txt.

#19 by David A. Corneth at Fri Nov 09 20:50:28 EST 2018

STATUS

editing

proposed

#18 by David A. Corneth at Fri Nov 09 20:49:39 EST 2018

LINKS

Robert Israel, David A. Corneth, <a href="/A115907/b115907_1.txt">Table of n, a(n) for n = 1..11241</a> (first 1000</a> from Robert Israel)

STATUS

approved

editing

Discussion

Fri Nov 09

20:50

David A. Corneth: extended b-file. Might want to dodge call to ithprime in prog.

#17 by Bruno Berselli at Thu Nov 08 10:57:43 EST 2018

STATUS

proposed

approved

#16 by Robert Israel at Thu Nov 08 10:48:59 EST 2018

STATUS

editing

proposed

#15 by Robert Israel at Thu Nov 08 10:48:44 EST 2018

LINKS

Robert Israel, <a href="/A115907/b115907.txt">Table of n, a(n) for n = 1..1000</a>

#14 by David A. Corneth at Thu Nov 08 09:35:12 EST 2018

PROG

(PARI) upto(n) = my(t = 0, res = List(), u = prime(n)); forprime(p = 2, n, u, t++; c = p + sigma(t); if(ispolygonal(c, 3), listput(res, t))); res \\ David A. Corneth, Nov 08 2018

#13 by David A. Corneth at Thu Nov 08 09:32:05 EST 2018

EXAMPLE

sigma(1880) +p prime(1880) = 20503 = T(202).

#12 by David A. Corneth at Thu Nov 08 09:30:40 EST 2018

PROG

(PARI) upto(n) = my(t = 0, res = List()); forprime(p = 2, n, t++; c = p + sigma(t); if(ispolygonal(c, 3), listput(res, t))); res \\ David A. Corneth, Nov 08 2018