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 A100963 a(1)=1. a(n) = a(n-1) + sum of the triangular numbers which are among the first (n-1) terms of the sequence. 3
 1, 2, 3, 7, 11, 15, 34, 53, 72, 91, 201, 311, 421, 531, 641, 751, 861, 1832, 2803, 3774, 4745, 5716, 6687, 7658, 8629, 9600, 10571, 11542, 12513, 13484, 14455, 15426, 16397, 17368, 18339, 19310, 20281, 21252, 22223, 23194, 24165, 25136, 26107, 27078, 28049 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Colin Barker, Table of n, a(n) for n = 1..1000 MATHEMATICA Nest[Append[#, Last@ # + Total@ Select[#, IntegerQ@ First@ Values@ Last@ Solve[x (x + 1)/2 == #, x] &]] &, {1}, 44] (* Michael De Vlieger, Sep 24 2017 *) PROG (PARI) vector(100, n, if(n==1, a_n_1=sum_=1, a_n_1+=sum_; if(ispolygonal(a_n_1, 3), sum_+=a_n_1)); a_n_1) \\ Colin Barker, Feb 19 2015 CROSSREFS Cf. A129895. Cf. A101135, A255260, A255261. Sequence in context: A092353 A189374 A180516 * A197636 A040103 A045323 Adjacent sequences:  A100960 A100961 A100962 * A100964 A100965 A100966 KEYWORD nonn AUTHOR Leroy Quet, Jun 07 2007 EXTENSIONS More terms from Robert Gerbicz, Jun 10 2007 STATUS approved

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Last modified January 24 16:47 EST 2020. Contains 331209 sequences. (Running on oeis4.)