A171463 The natural numbers excluding 2 and 3.

1, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74

Offset

1,2

Comments

Numbers k > 0 such that k*(k+1)/2 - 1 is nonprime. - Juri-Stepan Gerasimov, May 04 2010

Links

Table of n, a(n) for n=1..72.

Index entries for linear recurrences with constant coefficients, signature (2,-1).

Formula

a(n) = n + [n>1]*2.

Mathematica

Drop[Range[100], {2, 3}] (* Harvey P. Dale, May 05 2018 *)

Prog

(PARI) a(n)=if(n==1, 1, n+2) \\ Charles R Greathouse IV, Sep 02 2011

Crossrefs

Sequence in context: A114143 A171526 A359740 * A020705 A081313 A227983

Adjacent sequences: A171460 A171461 A171462 * A171464 A171465 A171466

Keyword

nonn,easy

Author

Juri-Stepan Gerasimov, Dec 09 2009, Dec 15 2009

Status

approved