A045803 3-ish numbers (end in 17, 19, 31, 33).
17, 19, 31, 33, 117, 119, 131, 133, 217, 219, 231, 233, 317, 319, 331, 333, 417, 419, 431, 433, 517, 519, 531, 533, 617, 619, 631, 633, 717, 719, 731, 733, 817, 819, 831, 833, 917, 919, 931, 933, 1017, 1019, 1031, 1033, 1117, 1119, 1131, 1133, 1217, 1219
Offset: 1
Links
- Reinhard Zumkeller, Table of n, a(n) for n = 1..1000
- Index entries for linear recurrences with constant coefficients, signature (1,0,0,1,-1).
Programs
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Haskell
import Data.List (findIndices) a045803 n = a045803_list !! (n-1) a045803_list = findIndices (`elem` [17,19,31,33]) $ cycle [0..99] -- Reinhard Zumkeller, Jan 23 2012
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Mathematica
Select[Range[1300],MemberQ[{17,19,31,33},Mod[#,100]]&] (* or *) LinearRecurrence[{1,0,0,1,-1},{17,19,31,33,117},50] (* Harvey P. Dale, Dec 17 2014 *) -
PARI
a(n) = -75/2 - (23*(-1)^n)/2 - (9-9*I)*(-I)^n - (9+9*I)*I^n + 25*n \\ Colin Barker, Oct 16 2015
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PARI
Vec(x*(17+2*x+12*x^2+2*x^3+67*x^4)/(1-x-x^4+x^5) + O(x^100)) \\ Colin Barker, Oct 16 2015
Formula
G.f.: x*(17+2*x+12*x^2+2*x^3+67*x^4)/(1-x-x^4+x^5). - Colin Barker, Jan 23 2012
a(n) = -75/2 - (23*(-1)^n)/2 - (9-9*i)*(-i)^n - (9+9*i)*i^n + 25*n where i=sqrt(-1). - Colin Barker, Oct 16 2015
Extensions
More terms from Erich Friedman