The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A193262 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A193262

Number of representations of 2*p_n as sum of two primes p,q such that p*q-2 is prime (p_n is the n-th prime).
(history; published version)

#35 by Alois P. Heinz at Wed Nov 11 08:29:39 EST 2020

STATUS

editing

approved

#34 by Alois P. Heinz at Wed Nov 11 08:29:00 EST 2020

KEYWORD

nonn,look,changed

STATUS

proposed

editing

#33 by Michel Marcus at Wed Nov 11 08:23:38 EST 2020

STATUS

editing

proposed

#32 by Michel Marcus at Wed Nov 11 08:23:35 EST 2020

PROG

(PARI) A193262(n, c=0)={ n=2*prime(n); forprime(p=1, n/2, isprime(n-p) || next; isprime(p*(n-p)-2) & c++); c} \\ - __M. F. Hasler_, Aug 06 2011

STATUS

proposed

editing

#31 by Jean-François Alcover at Wed Nov 11 08:23:07 EST 2020

STATUS

editing

proposed

#30 by Jean-François Alcover at Wed Nov 11 08:22:51 EST 2020

MATHEMATICA

a[n_] := Module[{t = 2 Prime[n], s = 0, p = 2, q}, While[True, q = t - p; If[q < p, Break[]]; If[PrimeQ[q] && PrimeQ[p q - 2], s++]; p = NextPrime[p]]; s];

Array[a, 100] (* Jean-François Alcover, Nov 11 2020, after Alois P. Heinz *)

STATUS

approved

editing

#29 by Alois P. Heinz at Fri Nov 14 09:21:08 EST 2014

STATUS

editing

approved

#28 by Alois P. Heinz at Fri Nov 14 09:21:04 EST 2014

MAPLE

seq (a(n), n=1..100); # Alois P. Heinz, Aug 04 2011

STATUS

approved

editing

#27 by Alois P. Heinz at Fri Nov 02 16:17:32 EDT 2012

STATUS

editing

approved

#26 by Alois P. Heinz at Fri Nov 02 16:17:27 EDT 2012

MAPLE

seq (a(n), n=1..100); # _Alois P. Heinz, _, Aug 04 2011

PROG

(PARI) A193262(n, c=0)={ n=2*prime(n); forprime(p=1, n/2, isprime(n-p) || next; isprime(p*(n-p)-2) & c++); c} \\ - _M. F. Hasler, _, Aug 06 2011

STATUS

approved

editing