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A132208 a(n) = 15n(n+1) + 11. 0
11, 41, 101, 191, 311, 461, 641, 851, 1091, 1361, 1661, 1991, 2351, 2741, 3161, 3611, 4091, 4601, 5141, 5711, 6311, 6941, 7601, 8291, 9011, 9761, 10541, 11351, 12191 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

The sequence starts with a string of primes for indices n = 0 to 6. a(n=7)=851 is composite, n=8 to 9 are prime, n=10 to 11 are composite etc. with an irregular pattern of primes/composites.

LINKS

Table of n, a(n) for n=0..28.

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

FORMULA

a(n) = 11 + 30*A000217(n). - Michel Marcus, Jun 24 2013

MATHEMATICA

Table[15n(n+1)+11, {n, 0, 40}] (* or *) LinearRecurrence[{3, -3, 1}, {11, 41, 101}, 40] (* Harvey P. Dale, Mar 01 2016 *)

PROG

(PARI) a(n) = 11 + 30*n*(n+1)/2 \\ Michel Marcus, Jun 24 2013

CROSSREFS

Sequence in context: A239462 A065145 A030685 * A233434 A261538 A066595

Adjacent sequences:  A132205 A132206 A132207 * A132209 A132210 A132211

KEYWORD

nonn,easy

AUTHOR

Nate Eskey (nj.eskey09(AT)bchigh.edu), Nov 06 2007

EXTENSIONS

Better definition from R. J. Mathar, Nov 16 2007

STATUS

approved

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Last modified June 15 16:13 EDT 2019. Contains 324142 sequences. (Running on oeis4.)