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 A119617 Integers of the form c(n)/b(n) where c(n+1)=c(n)+(n+1)^4 with c(0)=1 and b(n+1)=b(n)+(n+1)^2 with b(0)=1. 11
 1, 7, 25, 43, 79, 109, 163, 205, 277, 331, 421, 487, 595, 673, 799, 889, 1033, 1135, 1297, 1411, 1591, 1717, 1915, 2053, 2269, 2419, 2653, 2815, 3067, 3241, 3511, 3697, 3985, 4183, 4489, 4699, 5023, 5245, 5587, 5821, 6181, 6427, 6805, 7063, 7459, 7729 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The sequence is the union of A134153 and A134154 (without the first term of A134154): A134153(0)=1, A134154(1)=7, A134153(1)=25, A134154(2)=43, A134153(2)=79 and so on. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..10000 Index entries for linear recurrences with constant coefficients, signature (1,2,-2,-1,1). FORMULA From Bruno Berselli, Jun 27 2011: (Start) G.f.: x*(1+6*x+16*x^2+6*x^3+x^4)/((1+x)^2*(1-x)^3). a(n) = (30*n*(n-1)-3*(2*n-1)*(-1)^n+5)/8. (End) EXAMPLE c(0)/b(0) = 1/1 =1. c(3)/b(3) = (1+2^4+3^4)/(1+2^2+3^2)= (1+16+81)/(1+4+9) = 98/14 = 7. MAPLE P:=proc(n) local f, i, j, nu, de; nu:=0; de:=0; for i from 1 by 1 to n do nu:=nu+i^4; de:=de+i^2; f:=nu/de; if trunc(f)=f then print(f); fi; od; end: P(1000); MATHEMATICA LinearRecurrence[{1, 2, -2, -1, 1}, {1, 7, 25, 43, 79}, 50] (* Harvey P. Dale, Jan 21 2017 *) PROG From Bruno Berselli, Jun 27 2011: (Start) (Magma) [(30*n*(n-1)-3*(2*n-1)*(-1)^n+5)/8: n in [1..46]]; (PARI) for(n=1, 46, print1((30*n*(n-1)-3*(2*n-1)*(-1)^n+5)/8", ")); (Maxima) makelist((30*n*(n-1)-3*(2*n-1)*(-1)^n+5)/8, n, 1, 46); (End) CROSSREFS Cf. A000538, A000330. Sequence in context: A226366 A294459 A075927 * A102027 A031294 A147129 Adjacent sequences: A119614 A119615 A119616 * A119618 A119619 A119620 KEYWORD easy,nonn,changed AUTHOR Paolo P. Lava and Giorgio Balzarotti, Jun 06 2006 STATUS approved

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Last modified March 26 18:38 EDT 2023. Contains 361552 sequences. (Running on oeis4.)