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A171463 The natural numbers excluding 2 and 3. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers n such that n*(n+1)/2-1 is a nonnegative nonprime. [From 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

1 UNION A002808 UNION A169546.

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: A214084 A114143 A171526 * 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

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Last modified December 7 05:14 EST 2019. Contains 329839 sequences. (Running on oeis4.)