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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

There are infinitely many terms (see A214937 for a proof)

LINKS

Ivan N. Ianakiev, Table of n, a(n) for n = 1..1000

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

Cf. A000217, A000290, A214937

Sequence in context: A074232 A007417 A039099 * A035257 A235331 A175969

Adjacent sequences:  A215066 A215067 A215068 * A215070 A215071 A215072

KEYWORD

nonn

AUTHOR

Ivan N. Ianakiev, Aug 02 2012

STATUS

approved

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Last modified May 7 01:02 EDT 2021. Contains 343628 sequences. (Running on oeis4.)