A261935 - OEIS

A261935

The first of seventeen consecutive positive integers the sum of the squares of which is equal to the sum of the squares of two consecutive positive integers.

5, 23, 933, 2175, 65849, 152771, 4609041, 10692339, 322567565, 748311503, 22575121053, 52371113415, 1579935906689, 3665229628091, 110572938347721, 256513702853499, 7738525748434325, 17952293970117383, 541586229452055573, 1256404064205363855

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OFFSET

1,1

COMMENTS

For the first of the corresponding two consecutive positive integers, see A261933.

LINKS

Colin Barker, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (1,70,-70,-1,1).

FORMULA

G.f.: x*(21*x^4+18*x^3-560*x^2-18*x-5) / ((x-1)*(x^4-70*x^2+1)).

EXAMPLE

5 is in the sequence because 5^2 + 6^2 + ... + 21^2 = 40^2 + 41^2.