A289275 Numbers k such that the deficiency of k^2 is itself a square.

1, 2, 4, 8, 16, 32, 46, 64, 128, 256, 284, 512, 1024, 1633, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 149728, 242656, 260495, 262144, 298057, 524288, 1048576, 1056752, 2097152, 4194304, 8388608, 9587584, 16777216, 17706256, 33554432, 67108864, 134217728

Offset: 1

Author

Jens Voß, Jun 30 2017

Keywords

• nonn

Comments

The sequence of square roots of the deficiencies of this sequence is A288145.

The current sequence is the disjoint union of the powers of 2 (A000079) and the sequence A289274.

Links

• Giovanni Resta, Table of n, a(n) for n = 1..58

Crossrefs

Disjoint union of the sequences A000079 and A289274.

Square roots of deficiencies of squares is A288145.

Programs

Mathematica

Select[Range[10^5], IntegerQ@ Sqrt[2 #^2 - DivisorSigma[1, #^2]] &] (* Michael De Vlieger, Jul 04 2017 *)

PARI

isok(n) = issquare(2*n^2 - sigma(n^2)); \\ Michel Marcus, Jul 01 2017

Extensions

a(35)-a(38) from Giovanni Resta, Jul 27 2017