A241406 Numbers n such that n^2 == -1 (mod 61).
11, 50, 72, 111, 133, 172, 194, 233, 255, 294, 316, 355, 377, 416, 438, 477, 499, 538, 560, 599, 621, 660, 682, 721, 743, 782, 804, 843, 865, 904, 926, 965, 987, 1026, 1048, 1087, 1109, 1148, 1170, 1209, 1231, 1270, 1292, 1331, 1353, 1392, 1414, 1453, 1475, 1514
Offset: 1
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..1000
- Index entries for linear recurrences with constant coefficients, signature (1,1,-1).
Crossrefs
Cf. similar sequences listed in A155107.
Programs
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Magma
I:=[11,50,72]; [n le 3 select I[n] else Self(n-1)+Self(n-2)-Self(n-3): n in [1..50]];
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Magma
[-11*(-1)^n+61*Floor(n/2): n in [1..50]];
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Mathematica
Select[Range[1500], PowerMod[#, 2, 61] == 60 &] (* or *) CoefficientList[Series[(11 + 39 x + 11 x^2)/((1 + x) (1 - x)^2), {x, 0, 100}], x]
Formula
G.f.: x*(11 + 39*x + 11*x^2)/((1 + x)*(1 - x)^2).
a(n) = a(n-1) + a(n-2) - a(n-3) for n>2.
a(n) = a(n-2) + 61 for all n>2.
a(n) = -11*(-1)^n + 61*floor(n/2).
Comments