A215145 a(n) = 20*n + 1.
1, 21, 41, 61, 81, 101, 121, 141, 161, 181, 201, 221, 241, 261, 281, 301, 321, 341, 361, 381, 401, 421, 441, 461, 481, 501, 521, 541, 561, 581, 601, 621, 641, 661, 681, 701, 721, 741, 761, 781, 801, 821, 841, 861, 881, 901, 921, 941, 961, 981
Offset: 0
Links
- Jeremy Gardiner, Table of n, a(n) for n = 0..999
- Index entries for linear recurrences with constant coefficients, signature (2,-1).
Programs
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Magma
I:=[1,21]; [n le 2 select I[n] else 2*Self(n-1) - Self(n-2): n in [1..30]]; // G. C. Greubel, Apr 19 2018
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Mathematica
Range[1, 1001, 20] LinearRecurrence[{2, -1}, {1, 21}, 50] (* G. C. Greubel, Apr 19 2018 *) -
PARI
for(n=0, 50, print1(20*n + 1, ", ")) \\ G. C. Greubel, Apr 19 2018
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Scala
(1 to 1001 by 20).toList // Alonso del Arte, Feb 20 2020
Formula
From G. C. Greubel, Apr 19 2018: (Start)
a(n) = 2*a(n - 1) - a(n - 2).
G.f.: (1 + 19*x)/(1 - x)^2.
E.g.f.: (20*x + 1)*exp(x). (End)