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 A211013 Second 13-gonal numbers: a(n) = n*(11*n+9)/2. 6
 0, 10, 31, 63, 106, 160, 225, 301, 388, 486, 595, 715, 846, 988, 1141, 1305, 1480, 1666, 1863, 2071, 2290, 2520, 2761, 3013, 3276, 3550, 3835, 4131, 4438, 4756, 5085, 5425, 5776, 6138, 6511, 6895, 7290, 7696, 8113, 8541, 8980, 9430, 9891, 10363 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Sequence found by reading the line from 0, in the direction 0, 31... and the line from 10, in the direction 10, 63,..., in the square spiral whose vertices are the generalized 13-gonal numbers A195313. LINKS Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA G.f.: x(10+x)/(1-x)^3. - Philippe Deléham, Mar 27 2013 a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) with a(0) = 0, a(1) = 10, a(2) = 31. - Philippe Deléham, Mar 27 2013 a(n) = A051865(n) + 9n = A180223(n) + 8n = A022268(n) + 5n = A022269(n) + 4n = A152740(n) - n. - Philippe Deléham, Mar 27 2013 a(n) = A218530(11n+9). - Philippe Deléham, Mar 27 2013 PROG (PARI) a(n)=n*(11*n+9)/2 \\ Charles R Greathouse IV, Jun 17 2017 CROSSREFS Bisection of A195313. Second k-gonal numbers (k=5..14): A005449, A014105, A147875, A045944, A179986, A033954, A062728, A135705, this sequence, A211014. Cf. A051865. Sequence in context: A063154 A100500 A209994 * A085473 A051943 A059306 Adjacent sequences:  A211010 A211011 A211012 * A211014 A211015 A211016 KEYWORD nonn,easy AUTHOR Omar E. Pol, Aug 04 2012 STATUS approved

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Last modified November 20 06:06 EST 2018. Contains 317385 sequences. (Running on oeis4.)