The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A058377 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A058377

Number of solutions to 1 +- 2 +- 3 +- ... +- n = 0.
(history; published version)

#52 by Michael De Vlieger at Sat Feb 03 10:15:37 EST 2024

STATUS

reviewed

approved

#51 by Joerg Arndt at Sat Feb 03 00:25:21 EST 2024

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proposed

reviewed

#50 by Ilya Gutkovskiy at Thu Feb 01 06:00:39 EST 2024

STATUS

editing

proposed

#49 by Ilya Gutkovskiy at Thu Feb 01 05:48:58 EST 2024

FORMULA

a(n) = [x^n] Product_{k=1..n-1} (x^k + 1/x^k). - Ilya Gutkovskiy, Feb 01 2024

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approved

editing

#48 by Peter Luschny at Fri Nov 19 13:57:58 EST 2021

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proposed

approved

#47 by Jianing Song at Fri Nov 19 08:44:19 EST 2021

STATUS

editing

proposed

#46 by Jianing Song at Fri Nov 19 08:42:57 EST 2021

COMMENTS

a(n) is the coefficient of x^(n*(n+1)/4-1) of Product_{k=2..n} (1+x^k). - Jianing Song, Nov 19 2021

PROG

(PARI) list(n) = my(poly=vector(n), v=vector(n)); poly[1]=1; for(k=2, n, poly[k]=poly[k-1]*(1+'x^k)); for(k=1, n, if(k%4==1||k%4==2, v[k]=0, v[k]=polcoeff(poly[k], k*(k+1)/4-1))); v \\ Jianing Song, Nov 19 2021

CROSSREFS

Cf. A000217, A014601, A014494, A025591, A063865, A063866, A063867, A069918, A074378, A111133, A161943, A348639.

STATUS

approved

editing

#45 by N. J. A. Sloane at Mon Jul 29 15:07:36 EDT 2019

STATUS

editing

approved

#44 by N. J. A. Sloane at Mon Jul 29 15:07:34 EDT 2019

LINKS

Larry Glasser, <a href="/A058377/a058377.pdf">A formula for A058377</a>, Jul 29 2019

STATUS

approved

editing

#43 by Joerg Arndt at Thu Nov 16 06:42:28 EST 2017

STATUS

reviewed

approved