

A061722


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


3



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
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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

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]


FORMULA

a(n) = 10 * n^2 + 7.
G.f.: ( 7+4*x17*x^2 ) / (x1)^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



KEYWORD

easy,nonn


AUTHOR



EXTENSIONS



STATUS

approved



