A172462 Numbers k such that 2k-3, 2k-1, 2k+1 and 2k+3 are composite.

59, 60, 61, 72, 93, 102, 103, 108, 109, 123, 144, 149, 150, 151, 161, 162, 163, 171, 207, 213, 236, 237, 257, 258, 264, 265, 266, 267, 268, 276, 291, 312, 313, 318, 333, 334, 348, 357, 389, 390, 391, 396, 401, 402, 408, 417, 422, 423, 424, 434, 435, 436, 446

Offset

1,1

Comments

Almost all numbers are in this sequence, by the Prime Number Theorem.

Links

Table of n, a(n) for n=1..53.

Example

a(1)=59 because 2*59-1=117, 2*59+1=119, 2*59-3=115 and 2*59+3=121 are all composite.

Maple

a := proc (n): if isprime(2*n-3) = false and isprime(2*n-1) = false and isprime(2*n+1) = false and isprime(2*n+3) = false then n else end if end proc: seq(a(n), n = 1 .. 500); # Emeric Deutsch, Feb 15 2010

Crossrefs

Cf. A104278.

Sequence in context: A273183 A292093 A104916 * A042739 A348570 A172256

Adjacent sequences: A172459 A172460 A172461 * A172463 A172464 A172465

Keyword

nonn,easy,less

Author

Juri-Stepan Gerasimov, Feb 03 2010

Extensions

Corrected and extended by Emeric Deutsch, Feb 15 2010

Comment from Charles R Greathouse IV, Mar 25 2010

Status

approved