A243582 Integers of the form 8k+7 (A004771) that cannot be written as sum of four distinct squares.

7, 15, 23, 31, 47, 55, 103

Offset

1,1

Links

Table of n, a(n) for n=1..7.

J. O. Sizemore, Lagrange's Four Square Theorem

R. C. Vaughan, Lagrange's four-square theorem

Eric Weisstein's World of Math, Lagrange's Four-Square Theorem

Wikipedia, Lagrange's four-square theorem

Example

a(6) = 55 since 55 == 7 (mod 8) and all its representations as a sum of squares have duplicates, namely, 55=1^2+1^2+2^2+7^2, 55=1^2+2^2+5^2+5^2, 55=1^2+3^2+3^2+6^2.

Crossrefs

Cf. A001948, A004771, A008586, A016813, A016825, A004767, A243577, A243578, A243579, A243580, A243581.

Sequence in context: A029724 A194400 A177768 * A336819 A056828 A113505

Adjacent sequences: A243579 A243580 A243581 * A243583 A243584 A243585

Keyword

nonn,fini,full

Author

Walter Kehowski, Jun 08 2014

Status

approved