

A111051


Numbers m such that 3*m^2 + 1 is prime.


7



2, 6, 8, 12, 16, 20, 22, 26, 34, 36, 40, 58, 64, 68, 78, 82, 84, 86, 98, 112, 120, 126, 142, 146, 148, 152, 156, 160, 168, 188, 190, 194, 196, 208, 216, 218, 222, 238, 240, 244, 246, 254, 264, 272, 282, 286, 294, 300, 302, 306, 308, 316, 320, 330, 338, 344, 348
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OFFSET

1,1


COMMENTS

The resulting primes are the generalized cuban primes of the form (x^3y^3)/(xy), x=y+2 (see A002648).  Jani Melik, Jul 18 2007


LINKS



FORMULA



EXAMPLE

1 + 3*2^2 = 13 = A002648(1) is the 1st prime of this form, so a(1) = 2.
1 + 3*6^2 = 109 = A002648(2) is the 2nd prime of this form, so a(2) = 6.
1 + 3*8^2 = 193 = A002648(3) is the 3rd prime of this form, so a(3) = 8.
If m=98 then 3*m^2 + 1 = 28813 = A002648(19) is prime (the 19th of this form), so 98 is a term (the 19th).


MAPLE

ts_kubpra_ind:=proc(n) local i, tren, ans; ans:=[ ]: for i from 0 to n do tren:=1+3*i^2: if (isprime(tren)='true') then ans:=[ op(ans), i ] fi od: RETURN(ans); end: ts_kubpra_ind(2000); # Jani Melik, Jul 18 2007


MATHEMATICA



PROG



CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS



STATUS

approved



