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A106564 Perfect squares which are not the difference of two primes. 13
25, 49, 121, 169, 289, 361, 529, 625, 729, 841, 961, 1225, 1369, 1681, 1849, 2209, 2401, 2601, 2809, 3025, 3481, 3721, 3969, 4225, 4489, 4761, 5041, 5329, 5625, 5929, 6241, 6889, 7225, 7569, 7921, 8281, 8649, 9025, 9409, 10201, 10609, 11449, 11881 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..43.

FORMULA

n^2 - A106546 with 0's removed.

EXAMPLE

a(2)=49 because it is the second perfect square which is impossible to obtain subtracting a prime from

another one. 64 is not in the sequence because 64=67-3 (difference of two primes).

MATHEMATICA

With[{lst=Union[(#[[2]]-#[[1]])&/@Subsets[Prime[Range[2000]], {2}]]}, Select[Range[140]^2, !MemberQ[lst, #]&]] (* Harvey P. Dale, Jan 04 2011 *)

CROSSREFS

Cf. A106544-A106548, A106562-A106563, A106571, A106573-A106575, A106577.

Sequence in context: A110484 A110013 A109861 * A104777 A131706 A110015

Adjacent sequences:  A106561 A106562 A106563 * A106565 A106566 A106567

KEYWORD

easy,nonn

AUTHOR

Alexandre Wajnberg, May 09 2005

EXTENSIONS

Extended by Ray Chandler, May 12 2005

STATUS

approved

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Last modified October 30 07:54 EDT 2014. Contains 248796 sequences.