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 A198017 a(n) = n*(7*n + 11)/2 + 1. 11
 1, 10, 26, 49, 79, 116, 160, 211, 269, 334, 406, 485, 571, 664, 764, 871, 985, 1106, 1234, 1369, 1511, 1660, 1816, 1979, 2149, 2326, 2510, 2701, 2899, 3104, 3316, 3535, 3761, 3994, 4234, 4481, 4735, 4996, 5264, 5539, 5821, 6110, 6406, 6709, 7019, 7336, 7660, 7991 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS First bisection of A193053 (see also the numerical spiral illustrated in the Links section). The inverse binomial transform yields 1, 9, 7, 0, 0 (0 continued). The subsequence of primes begins: 79, 211, 269, 571, 1511, 1979, 3761, 4481, 5821, 6709, 7019. [Jonathan Vos Post, Oct 21 2011] LINKS Bruno Berselli, Table of n, a(n) for n = 0..1000 Bruno Berselli, Illustration of initial terms. Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA G.f.: (1+7*x-x^2)/(1-x)^3. a(n) = A195020(2n) + 2n + 1. a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) = 2*a(n-1) - a(n-2) + 7. MATHEMATICA Table[(n(7n+11))/2+1, {n, 0, 60}] (* or *) LinearRecurrence[{3, -3, 1}, {1, 10, 26}, 60] (* Harvey P. Dale, Mar 03 2013 *) PROG (PARI) for(n=0, 47, print1(n*(7*n+11)/2+1", ")); (Magma) [n*(7*n+11)/2+1: n in [0..47]]; CROSSREFS Cf. A195020 (vertices of the numerical spiral in link). Cf. A017005 (first differences). Cf. A069099, A001106. Cf. A001106, A022264, A033572, A144555, A152760, A158482, A158485, A185019, A193053, A195021, A195023-A195030, A195320 [incomplete list]. Sequence in context: A229309 A044452 A299409 * A137351 A134406 A099978 Adjacent sequences: A198014 A198015 A198016 * A198018 A198019 A198020 KEYWORD nonn,easy AUTHOR Bruno Berselli, Oct 21 2011 - based on remarks and sequences by Omar E. Pol STATUS approved

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Last modified January 30 07:42 EST 2023. Contains 359942 sequences. (Running on oeis4.)