A053678 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 k values.

5, 17, 191, 1412, 2143, 8393, 5346, 32475, 99234, 158712, 393981, 401023, 514617, 921485, 577350, 910495, 1430793, 3236406, 462236, 4122855

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 k-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]; A053678 = Table[res = {i, j, k} /. ToRules[r[i]]; Print[res]; res, {i, A053676}][[All, 3]] (* Jean-François Alcover, Dec 07 2012 *)

Crossrefs

i values are A053676 and j values are A053677.

Sequence in context: A097490 A355277 A164740 * A090645 A206328 A096407

Adjacent sequences: A053675 A053676 A053677 * A053679 A053680 A053681

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