A262017 The first of five consecutive positive integers the sum of the squares of which is equal to the sum of the squares of six consecutive positive integers.
61, 1381, 30361, 666601, 14634901, 321301261, 7053992881, 154866542161, 3400009934701, 74645352021301, 1638797734533961, 35978904807725881, 789897108035435461, 17341757471971854301, 380728767275345359201, 8358691122585626048161, 183510475929608427700381
Offset: 1
Examples
61 is in the sequence because 61^2 + ... + 65^2 = 19855 = 55^2 + ... + 60^2.
Links
- Colin Barker, Table of n, a(n) for n = 1..744
- Index entries for linear recurrences with constant coefficients, signature (23,-23,1).
Programs
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PARI
Vec(-x*(x^2-22*x+61)/((x-1)*(x^2-22*x+1)) + O(x^40))
Formula
a(n) = 23*a(n-1)-23*a(n-2)+a(n-3) for n>3.
G.f.: -x*(x^2-22*x+61) / ((x-1)*(x^2-22*x+1)).
Comments