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A215069
Natural numbers that when squared can be expressed as sums of a positive square number and a positive triangular number
1
2, 4, 5, 7, 8, 9, 10, 11, 13, 14, 16, 17, 19, 20, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 34, 35, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 49, 50, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 79, 80, 82, 83, 84, 85
OFFSET
1,1
COMMENTS
There are infinitely many terms (see A214937 for a proof)
LINKS
FORMULA
a(n) = sqrt(A214937(n))
EXAMPLE
2 and 7 are in the sequence because 2^2=1^2+2*3/2 and 7^2=2^2+9*10/2
CROSSREFS
KEYWORD
nonn
AUTHOR
Ivan N. Ianakiev, Aug 02 2012
STATUS
approved