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A076463
Sum of squares of numbers that can be written as t*n + u*(n+1) for nonnegative integers t,u in exactly four ways.
1
85, 2803, 24026, 115270, 397655, 1107505, 2653588, 5685996, 11176665, 20511535, 35594350, 58962098, 93912091, 144640685, 216393640, 315628120, 450186333, 629480811, 864691330, 1168973470, 1557678815, 2048586793, 2662148156, 3421740100, 4353933025
OFFSET
1,1
REFERENCES
Fred. Schuh, Vragen betreffende een onbepaalde vergelijking, Nieuw Tijdschrift voor Wiskunde, 52 (1964-1965) 193-198.
LINKS
FORMULA
a(n) = n*(n+1)*(97*n^4+146*n^3+30*n^2-19*n+1)/6.
G.f.: x*(85+2208*x+6190*x^2+2976*x^3+181*x^4)/(1-x)^7.
MAPLE
seq(1/6*n*(n+1)*(97*n^4+146*n^3+30*n^2-19*n+1), n=1..30);
MATHEMATICA
CoefficientList[Series[(85 + 2208 x + 6190 x^2 + 2976 x^3 + 181 x^4)/(1 - x)^7, {x, 0, 50}], x] (* Vincenzo Librandi, Dec 30 2013 *)
PROG
(Magma) [n*(n+1)*(97*n^4+146*n^3+30*n^2-19*n+1)/6: n in [1..50]]; // Vincenzo Librandi, Dec 30 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Floor van Lamoen, Oct 13 2002
STATUS
approved