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A215801

Prime numbers p such that (2^p + 1)/3 can be written in the form a^2 + 3*b^2.

3, 7, 13, 19, 31, 37, 43, 61, 67, 73, 79, 109, 127, 139, 151, 199, 277, 313, 433, 457, 547, 613, 619, 643, 739, 967

OFFSET

1,1

COMMENTS

These (2^p + 1)/3 numbers have no prime factors of the form 2 (mod 3) to an odd power.

LINKS

Samuel S. Wagstaff, Jr., The Cunningham Project, Factorizations of 2^n-1, for odd n's < 1200

PROG

(PARI) forprime(i=2, 100, a=factorint(2^i+1)~; has=0; for(j=1, #a, if(a[1, j]%3==2&&a[2, j]%2==1, has=1; break)); if(has==0, print(i" -\t"a[1, ])))

CROSSREFS

KEYWORD

nonn

AUTHOR

V. Raman, Aug 23 2012

EXTENSIONS

9 more terms from V. Raman, Aug 28 2012

STATUS

approved

URL: https://oeis.org/A215801