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A233998 Values of n such that numbers of the form x^2+n*y^2 for some integers x, y cannot have prime factor of 5 raised to an odd power. 3
2, 3, 7, 8, 12, 13, 17, 18, 22, 23, 27, 28, 32, 33, 37, 38, 42, 43, 47, 48, 50, 52, 53, 57, 58, 62, 63, 67, 68, 72, 73, 75, 77, 78, 82, 83, 87, 88, 92, 93, 97, 98, 102, 103, 107, 108, 112, 113, 117, 118, 122, 123, 127, 128, 132, 133, 137, 138, 142, 143, 147, 148, 152, 153, 157, 158 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Equivalently, this sequence is the union of numbers of the form 25^n*(5*n+2) and numbers of the form 25^n*(5*n+3).

LINKS

Table of n, a(n) for n=1..66.

FORMULA

a(n) = 2.4 n + O(log n). - Charles R Greathouse IV, Dec 19 2013

PROG

(PARI) is(n)=n/=25^valuation(n, 25); n%5==2||n%5==3 \\ Charles R Greathouse IV and V. Raman, Dec 19 2013

CROSSREFS

Cf. A055046, A055047, A233999.

Sequence in context: A214324 A102664 A055053 * A047221 A331078 A032967

Adjacent sequences:  A233995 A233996 A233997 * A233999 A234000 A234001

KEYWORD

nonn,easy

AUTHOR

V. Raman, Dec 18 2013

STATUS

approved

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Last modified May 11 21:35 EDT 2021. Contains 343808 sequences. (Running on oeis4.)