A076457 Sum of numbers that can be written as t*n + u*(n+1) for nonnegative integers t,u in exactly four ways.

13, 129, 534, 1510, 3435, 6783, 12124, 20124, 31545, 47245, 68178, 95394, 130039, 173355, 226680, 291448, 369189, 461529, 570190, 696990, 843843, 1012759, 1205844, 1425300, 1673425, 1952613, 2265354, 2614234, 3001935, 3431235, 3905008, 4426224, 4997949, 5623345

Offset

1,1

References

Fred. Schuh, Vragen betreffende een onbepaalde vergelijking, Nieuw Tijdschrift voor Wiskunde, 52 (1964-1965) 193-198.

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Formula

a(n) = n*(n+1)*(8*n^2+6*n-1)/2.

G.f.: x*(13+64*x+19*x^2)/(1-x)^5.

Maple

seq(1/2*n*(n+1)*(8*n^2+6*n-1), n=1..40);

Mathematica

CoefficientList[Series[(13 + 64 x + 19 x^2)/(1 - x)^5, {x, 0, 50}], x] (* Vincenzo Librandi, Dec 30 2013 *)

Prog

(Magma) [n*(n+1)*(8*n^2+6*n-1)/2: n in [1..50]]; // Vincenzo Librandi, Dec 30 2013

Crossrefs

Cf. A002417, A076454-A076459.

Sequence in context: A361068 A211897 A147669 * A227749 A016162 A155623

Adjacent sequences: A076454 A076455 A076456 * A076458 A076459 A076460

Keyword

nonn,easy

Author

Floor van Lamoen, Oct 13 2002

Status

approved