A061722 a(n) = 10 * n^2 + 7.

7, 17, 47, 97, 167, 257, 367, 497, 647, 817, 1007, 1217, 1447, 1697, 1967, 2257, 2567, 2897, 3247, 3617, 4007, 4417, 4847, 5297, 5767, 6257, 6767, 7297, 7847, 8417, 9007, 9617, 10247, 10897, 11567, 12257, 12967, 13697, 14447, 15217, 16007, 16817

Offset

0,1

Comments

Initially this sequence is rich in primes. First 7 terms are all prime numbers. But the 8th term 491 is a composite number equal to 7 * 71. The first 28 terms are primes or semiprimes. - Kausthub Gudipati, Sep 25 2011

Links

Harry J. Smith, Table of n, a(n) for n = 0..1000

T. Trotter, Jr, Trotter Numbers & Trotter Primes [Warning: As of March 2018 this site appears to have been hacked. Proceed with great caution. The original content should be retrieved from the Wayback machine and added here. - N. J. A. Sloane, Mar 29 2018]

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

Formula

a(n) = 10 * n^2 + 7.

G.f.: ( -7+4*x-17*x^2 ) / (x-1)^3 . - R. J. Mathar, Feb 27 2015

Prog

(PARI) { for (n=1, 1000, write("b061722.txt", n, " ", 10*n^2 + 7) ) } \\ Harry J. Smith, Jul 27 2009

Crossrefs

Cf. A061679, A195905.

Sequence in context: A179030 A179031 A107178 * A195905 A104164 A192244

Adjacent sequences: A061719 A061720 A061721 * A061723 A061724 A061725

Keyword

easy,nonn

Author

Terrel Trotter, Jr., Jun 20 2001

Extensions

Definition revised by Omar E. Pol, Aug 04 2009

Status

approved