The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A361670 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A361670

Squarefree part of the n-th triangular number.
(history; published version)

#14 by Peter Luschny at Thu Mar 23 03:45:18 EDT 2023

STATUS

reviewed

approved

#13 by Joerg Arndt at Thu Mar 23 03:08:13 EDT 2023

STATUS

proposed

reviewed

#12 by Michel Marcus at Wed Mar 22 12:58:40 EDT 2023

STATUS

editing

proposed

#11 by Michel Marcus at Wed Mar 22 12:58:34 EDT 2023

COMMENTS

a(n) = 1 for n >0 in A001108. - Michel Marcus, Mar 22 2023

#10 by Michel Marcus at Wed Mar 22 12:57:29 EDT 2023

COMMENTS

a(n) = 1 for n in A001108. - Michel Marcus, Mar 22 2023

PROG

(PARI) a(n) = core(n*(n+1)/2); \\ Michel Marcus, Mar 22 2023

CROSSREFS

Cf. A000217, A007913, A083481 (of oblong num.), A361671 (of tetrah. num.tetrahedral).

Cf. A001108, A039963.

STATUS

approved

editing

#9 by Alois P. Heinz at Mon Mar 20 10:10:02 EDT 2023

STATUS

editing

approved

#8 by Alois P. Heinz at Mon Mar 20 10:09:59 EDT 2023

MAPLE

a:= n-> mul(i[1]^irem(i[2], 2), i=ifactors(n*(n+1)/2)[2]):

seq(a(n), n=1..70); # Alois P. Heinz, Mar 20 2023

STATUS

proposed

editing

#7 by Chai Wah Wu at Mon Mar 20 09:59:34 EDT 2023

STATUS

editing

proposed

#6 by Chai Wah Wu at Mon Mar 20 09:59:26 EDT 2023

PROG

(Python)

from sympy.ntheory.factor_ import core

def A361670(n): return core(n*(n+1)>>1) # Chai Wah Wu, Mar 20 2023

STATUS

approved

editing

#5 by R. J. Mathar at Mon Mar 20 07:37:09 EDT 2023

STATUS

editing

approved