A091300 Nonprimes of the form 6k + 1.

1, 25, 49, 55, 85, 91, 115, 121, 133, 145, 169, 175, 187, 205, 217, 235, 247, 253, 259, 265, 289, 295, 301, 319, 325, 343, 355, 361, 385, 391, 403, 415, 427, 445, 451, 469, 475, 481, 493, 505, 511, 517, 529, 535, 553, 559, 565, 583, 589, 595, 625, 637, 649

Offset: 1

Author

Labos Elemer, Feb 24 2004

Keywords

• easy
• nonn

References

• R. K. Guy, Unsolved Problems in Number Theory, Springer, 1st edition, 1981. See section D1.

Links

• Nathaniel Johnston, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A091113, A092256.

Cf. A002476. Subsequence of A016921.

Programs

GAP

Filtered(List([0..110],k->6*k+1),n->not IsPrime(n)); # Muniru A Asiru, Mar 12 2019

Maple

for k from 0 to 100 do if(not isprime(6*k+1))then printf("%d, ",6*k+1); fi: od: # Nathaniel Johnston, May 18 2011

Mathematica

Do[If[ !PrimeQ[n]&&Equal[Mod[n, 6], 1 ], Print[n]], {n, 1, 1000}]
DeleteCases[6*Range[0,150]+1,?PrimeQ] (* _Harvey P. Dale, Jun 23 2014 *)

Sage

[n for n in (1..650) if ((n-1)/6).is_integer() and not is_prime(n)] # Stefano Spezia, Oct 05 2024