A053677 Let Oc(n) = A005900(n) = n-th octahedral number. Consider all integer triples (i,j,k), j >= k > 0, with Oc(i) = Oc(j)+Oc(k), ordered by increasing i; sequence gives j values.

6, 40, 454, 2600, 2586, 20175, 48103, 93097, 105805, 265195, 755100, 803007, 1211000, 1111974, 1493421, 1499160, 2622000, 4309280, 5127195, 5574139

Offset

1,1

Links

Table of n, a(n) for n=1..20.

Example

Oc(7) = 231 = Oc(6) + Oc(5); Oc(41) = 45961 = Oc(40) + Oc(17); Oc(465) = 67029905 = Oc(454) + Oc(191)

Mathematica

(* This is just a check of j-values, given i-values *) A053676 = {7, 41, 465, 2732, 3005, 20648, 48125, 94396, 129299, 282931, 789281, 835050, 1241217, 1292143, 1521647, 1603655, 2756953, 4847702, 5128447, 6242598}; r[i_] := Reduce[0 < k <= j && 2*i^3 + i == 2*j^3 + j + 2*k^3 + k, {j, k}, Integers]; A053677 = Table[res = {i, j, k} /. ToRules[r[i]]; Print[res]; res, {i, A053676}][[All, 2]] (* Jean-François Alcover, Dec 07 2012 *)

Crossrefs

i values are A053676 and k values are A053678.

Sequence in context: A143342 A084270 A284195 * A204563 A356540 A374867

Adjacent sequences: A053674 A053675 A053676 * A053678 A053679 A053680

Keyword

nice,nonn

Author

Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Feb 16 2000

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), May 07 2001

a(13)-a(16) from Donovan Johnson, Jun 21 2010

a(17)-a(20) from Donovan Johnson, Sep 29 2010

Status

approved