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 A253208 a(n) = 4^n + 3. 7
 4, 7, 19, 67, 259, 1027, 4099, 16387, 65539, 262147, 1048579, 4194307, 16777219, 67108867, 268435459, 1073741827, 4294967299, 17179869187, 68719476739, 274877906947, 1099511627779, 4398046511107, 17592186044419, 70368744177667, 281474976710659 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Subsequence of A226807. LINKS Index entries for linear recurrences with constant coefficients, signature (5,-4). FORMULA G.f.: (4 - 13*x)/((1 - x)*(1 - 4*x)). a(n) = 5*a(n-1) - 4*a(n-2) for n>1. MATHEMATICA Table[4^n + 3, {n, 0, 30}] (* or *) CoefficientList[Series[(4 - 13 x) / ((1 - x) (1 - 4 x)), {x, 0, 40}], x] PROG (MAGMA) [4^n+3: n in [0..30]]; (PARI) a(n)=4^n+3 \\ Charles R Greathouse IV, Oct 07 2015 CROSSREFS Cf. numbers of the form k^n+k-1: A000057 (k=2), A168607 (k=3), this sequence (k=4), A242329 (k=5), A253209 (k=6), A253210 (k=7), A253211 (k=8), A253212 (k=9), A253213 (k=10). Cf. A141725, A226807. Sequence in context: A220011 A305034 A133264 * A275389 A127415 A045548 Adjacent sequences:  A253205 A253206 A253207 * A253209 A253210 A253211 KEYWORD nonn,easy AUTHOR Vincenzo Librandi, Dec 29 2014 STATUS approved

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Last modified August 4 02:10 EDT 2020. Contains 336201 sequences. (Running on oeis4.)