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A257292 Numbers whose square can be written as the sum of two consecutive nonsquares. 1
5, 9, 11, 13, 15, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Equivalently, odd numbers such that neither of the two integers next to n^2/2 is a square.

Complement of A257282 = square roots of A256944.

The odd numbers missing here are 1, 3, 7, 17, 41, 99, ... = A078057 (see also A001333 = abs(A123335)).

LINKS

Table of n, a(n) for n=1..60.

EXAMPLE

9 is a term because 9^2 = 81 = 40 + 41, neither of which are square.

MATHEMATICA

Select[Range[1, 131, 2], AllTrue[{Floor[#^2/2], Ceiling[#^2/2]}, ! IntegerQ@ Sqrt@ # &] &] (* Michael De Vlieger, Dec 11 2015, Version 10 *)

PROG

(PARI) is(n)={bittest(n, 0) && !issquare(n^2\2) && !issquare(n^2\2)

CROSSREFS

Cf. A001333, A078057, A123335, A257282.

Sequence in context: A101731 A080765 A226039 * A234285 A314584 A294277

Adjacent sequences:  A257289 A257290 A257291 * A257293 A257294 A257295

KEYWORD

nonn

AUTHOR

M. F. Hasler, May 08 2015

STATUS

approved

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Last modified July 22 14:46 EDT 2019. Contains 325224 sequences. (Running on oeis4.)