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A257772 Numbers n>=0 such that (n+1)^3 - n^3 = 3*n^2+3*n+1 is not prime. 1
0, 5, 7, 8, 12, 15, 16, 18, 19, 20, 21, 22, 26, 29, 31, 33, 35, 36, 39, 40, 43, 44, 46, 47, 50, 51, 53, 54, 56, 57, 59, 60, 61, 64, 65, 68, 69, 70, 71, 72, 73, 75, 76, 77, 78, 79, 82, 83, 84, 85, 87, 89, 92, 94, 96, 97, 98, 99, 100, 101, 102, 103, 104, 106 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Complement of A111251.

Includes all members of A047383 except 1. - Robert Israel, May 12 2015

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

FORMULA

a(n) ~ n. - Charles R Greathouse IV, May 22 2015

EXAMPLE

5 is a term since (5+1)^3 - 5^3 = 91 = 13*7 is not prime.

MAPLE

remove(t -> isprime((t+1)^3-t^3), [$0..300]); # Robert Israel, May 12 2015

MATHEMATICA

Select[Range[0, 200], ! PrimeQ[(#+1)^3 - #^3] &] (* Giovanni Resta, May 08 2015 *)

PROG

(UBASIC)

10 print 0

20 for n=1 to 200

30   s = (n+1)^3 - n^3

40   if prmdiv(s)<>s then print n

50 next n

(MAGMA) [n: n in [0..120] | not IsPrime(3*n^2+3*n+1)]; // Vincenzo Librandi, May 13 2015

(PARI) for(n=0, 100, if(!isprime(3*n^2+3*n+1), print1(n, ", "))) \\ Derek Orr, May 19 2015

CROSSREFS

Cf. A003215, A047383, A111251.

Sequence in context: A173664 A171420 A047384 * A314374 A066001 A320391

Adjacent sequences:  A257769 A257770 A257771 * A257773 A257774 A257775

KEYWORD

nonn,easy

AUTHOR

Miguel Angel Velilla Mula, May 08 2015

STATUS

approved

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Last modified March 7 13:24 EST 2021. Contains 341886 sequences. (Running on oeis4.)