The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A136346

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

A136346

Octagonal numbers which are the sums of exactly two positive octagonal numbers.
(history; published version)

#13 by Harvey P. Dale at Sat Oct 26 16:24:33 EDT 2019

STATUS

editing

approved

#12 by Harvey P. Dale at Sat Oct 26 16:24:30 EDT 2019

MATHEMATICA

Module[{nn=300, ono}, ono=PolygonalNumber[8, Range[nn]]; Union[Select[ Total/@ Tuples[ono, 2], MemberQ[ono, #]&]]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Oct 26 2019 *)

STATUS

approved

editing

#11 by Alois P. Heinz at Fri Feb 02 15:04:28 EST 2018

STATUS

proposed

approved

#10 by Andrew Howroyd at Fri Feb 02 13:13:44 EST 2018

STATUS

editing

proposed

#9 by Andrew Howroyd at Fri Feb 02 12:59:21 EST 2018

LINKS

B. D. Swan, <a href="/A136346/b136346.txt">Table of n, a(n) for n = 01..1800</a>

STATUS

approved

editing

#8 by N. J. A. Sloane at Sun Dec 25 02:18:21 EST 2016

STATUS

proposed

approved

#7 by Jon E. Schoenfield at Sun Dec 25 00:59:10 EST 2016

STATUS

editing

proposed

#6 by Jon E. Schoenfield at Sun Dec 25 00:59:07 EST 2016

COMMENTS

For sums of two positive octagonal numbers, see: A136345. This is to octagonal numbers A000567 as A089982 is to triangular numbers A000217 and , as A009000 is to squares A000290 and , as A136117 are is to pentagonal numbers A000326) and , as A133215 is to hexagonal numbers A000384 , and as A117104 is to heptagonal numbers A000566. If Oc(a) + Oc(b) = Oc(c) then a(3a-2) + b(3b+2) = c(3c+2), so solving the quadrataic quadratic equations for c we have (when an integer): c = (2 + SQRTsqrt(4 + 36a^2 + 36b^2 - 24a - 24b))/6.

LINKS

B. D. Swan, <a href="/A136346/b136346.txt">Table of n, a(n) for n = 0,...,1800</a>

STATUS

approved

editing

#5 by Russ Cox at Fri Mar 30 18:40:44 EDT 2012

AUTHOR

_Jonathan Vos Post (jvospost3(AT)gmail.com), _, Dec 25 2007

Discussion

Fri Mar 30

18:40

OEIS Server: https://oeis.org/edit/global/228

#4 by N. J. A. Sloane at Thu Nov 11 07:34:06 EST 2010

LINKS

B. D. Swan, <a href="/A136346/b136346.txt">Table of n, a(n) for n=0,...,1800</a>

KEYWORD

easy,nonn,new