

A275708


a(1)=1, a(2)=2; thereafter a(n) is the smallest positive integer not yet used such that a(n)+a(n1)a(n2) is a square.


0



1, 2, 3, 8, 4, 5, 15, 6, 10, 12, 7, 9, 14, 11, 19, 17, 18, 24, 30, 43, 23, 21, 27, 58, 33, 26, 16, 35, 45, 39, 22, 42, 29, 38, 40, 34, 31, 28, 52, 25, 36, 53, 32, 37, 20, 66, 54, 13, 50, 44, 55, 70, 49, 46, 67
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OFFSET

1,2


COMMENTS

Apparently this is a permutation of positive numbers. Out of the first 10000 terms the missing numbers are:
8974, 9298, 9342, 9380, 9386, 9425, 9429, 9454, 9495, 9497, 9525,...,
while the maximal term is a(9919)=10802.
Corresponding squares:
4, 9, 9, 1, 16, 16, 1, 16, 9, 4, 16, 16, 16, 25, 16, 25, 36, 49, 36, 1, 25, 64, 64, 1, ...


LINKS

Table of n, a(n) for n=1..55.


EXAMPLE

1+2+3=4, 2+3+8=9, 3+8+4=9.


MATHEMATICA

s={1, 2}; Do[a = s[[1]]  s[[2]]; k = 1; While[(b=k^2a)<=0  MemberQ[s, b], k++]; AppendTo[s, k^2  a], {100}]; s


CROSSREFS

Cf. A076991.
Sequence in context: A328428 A195794 A145605 * A111809 A100869 A110142
Adjacent sequences: A275705 A275706 A275707 * A275709 A275710 A275711


KEYWORD

nonn


AUTHOR

Zak Seidov, Aug 06 2016


STATUS

approved



