

A140612


Positive integers k such that both k and k+1 are the sum of 2 squares.


4



1, 4, 8, 9, 16, 17, 25, 36, 40, 49, 52, 64, 72, 73, 80, 81, 89, 97, 100, 116, 121, 136, 144, 145, 148, 169, 180, 193, 196, 225, 232, 233, 241, 244, 256, 260, 288, 289, 292, 305, 313, 324, 337, 360, 361, 369, 388, 400, 404, 409, 424, 441, 449, 457
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OFFSET

1,2


COMMENTS

Equivalently, positive k such that k*(k+1) is the sum of two squares.
Trivially, sequence includes all positive squares.


LINKS

Table of n, a(n) for n=1..54.


EXAMPLE

40 = 6^2 + 2^2, 41 = 5^2 + 4^2, so 40 is in the sequence.


CROSSREFS

Cf. A050795 (2*a(n)+1), A001481, A002378, A000290.
Sequence in context: A153034 A106840 A242663 * A160053 A225353 A034023
Adjacent sequences: A140609 A140610 A140611 * A140613 A140614 A140615


KEYWORD

nonn,easy


AUTHOR

Franklin T. AdamsWatters, May 19 2008


STATUS

approved



