A139220 Numbers k such that 41+(k+k^2)/2 = 41+A000217(k) is prime.

0, 3, 11, 20, 23, 27, 32, 39, 44, 48, 51, 56, 59, 60, 83, 104, 108, 111, 116, 128, 132, 135, 143, 171, 188, 203, 207, 212, 227, 240, 251, 263, 275, 296, 300, 312, 315, 324, 356, 359, 363, 380, 384, 392, 399, 408, 443, 447, 476, 479, 483, 504, 507, 515, 527, 528

Offset

1,2

Comments

Corresponding values of primes are in A139219.

Numbers k such that both 41+(k+k^2)/2 and 41+(k+k^2) are primes, are in A139221.

Links

Table of n, a(n) for n=1..56.

Example

If k = 11 then 41 + (k + k^2) / 2 = 107 (prime).

Mathematica

Select[Table[Range[0, 1000]], PrimeQ[41+(#+#^2)/2]&]

Prog

(PARI) is(n)=isprime(n*(n+1)/2+41) \\ Charles R Greathouse IV, Aug 16 2015
(Magma) [k:k in [0..530]| IsPrime(41+(k+k^2) div 2)]; // Marius A. Burtea, Feb 12 2020

Crossrefs

Cf. A000217, A056561, A139219, A139221.

Sequence in context: A082628 A279257 A166096 * A139221 A300381 A363012

Adjacent sequences: A139217 A139218 A139219 * A139221 A139222 A139223

Keyword

nonn

Author

Zak Seidov, Apr 11 2008

Status

approved