A136478 - OEIS

A136478

Smallest y such that for x = A136477(n), x^2 + x + y^2 is an odd primitive abundant number, A136476(n).

7, 7, 3, 15, 15, 15, 7, 3, 5, 7, 3, 15, 15, 27, 3, 15, 3, 27, 15, 27, 13, 3, 49, 17, 55, 27, 27, 15, 53, 77, 63, 77, 15, 45, 15, 69, 45, 77, 15, 57, 75, 27, 75, 63, 55, 75, 49, 85, 7, 3

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OFFSET

1,1

COMMENTS

See A136477 and A136476 for the x-values and the abundant numbers x^2 + x + y^2.

LINKS

Table of n, a(n) for n=1..50.

FORMULA

a(n) = sqrt(A136476(n) - A136477(n)^2 - A136477(n)). - M. F. Hasler, Feb 22 2017

EXAMPLE

97^2+97+7^2 = 9555 = A136476(1) is an odd primitive abundant number, therefore a(1) = 7.

PROG

(PARI) {for(x=1, 5000, my(n=x^2+x+1, f); forstep(y=1, sqrtint(2*x), 2, sigma(n+=y*4-4, -1)>2 || next; for(i=1, #f=factor(n)[, 1], sigma(n\f[i], -1)>2 && next(2)); print1(y", "); break))} \\ M. F. Hasler, Feb 22 2017

CROSSREFS

Cf. A006038, A136476, A136477, A136479.

Sequence in context: A153204 A199508 A378003 * A097903 A221566 A064619

Adjacent sequences: A136475 A136476 A136477 * A136479 A136480 A136481

KEYWORD

nonn

AUTHOR

Pierre CAMI, Dec 31 2007

EXTENSIONS

Edited by M. F. Hasler, Feb 22 2017

STATUS

approved