The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A051867

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A051867

15-gonal (or pentadecagonal) numbers: n*(13n-11)/2.
(history; published version)

#57 by N. J. A. Sloane at Tue Jun 11 09:33:19 EDT 2024

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proposed

approved

#56 by Michel Marcus at Tue May 21 12:49:40 EDT 2024

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editing

proposed

#55 by Michel Marcus at Tue May 21 12:48:57 EDT 2024

NAME

15-gonal (or pentadecagonal) numbers: n*(13n-11)/2.

STATUS

proposed

editing

#54 by Charlie Marion at Tue May 21 12:14:24 EDT 2024

STATUS

editing

proposed

#53 by Charlie Marion at Tue May 21 12:14:14 EDT 2024

FORMULA

a(n) = A000326(3*n-2) - 7*(n-1)^2. In general, if we let P(k,n) = the n-th k-gonal number, then P(5*k,n) = P(5,k*n-k+1) - A005449(k-1)*(n-1)^2. More generally, if we let SP(k,n) = the n-th second k-gonal number, then for m>2 and k>0, P(m*k,n) = P(m,k*n-k+1) - SP(m,k-1)*(n-1)^2. - Charlie Marion, May 21 2024

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approved

editing

#52 by Joerg Arndt at Mon Feb 06 08:04:09 EST 2023

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reviewed

approved

#51 by Alois P. Heinz at Mon Feb 06 07:56:37 EST 2023

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proposed

reviewed

#50 by Nikolaos Pantelidis at Mon Feb 06 07:11:24 EST 2023

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editing

proposed

#49 by Nikolaos Pantelidis at Mon Feb 06 07:11:21 EST 2023

FORMULA

E.g.f.: exp(x)*(x + 13*x^2/2). - Nikolaos Pantelidis, Feb 06 2023

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approved

editing

#48 by Michel Marcus at Thu Jan 21 04:15:11 EST 2021

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reviewed

approved