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A237835 a(n) = n*(Pisano period of n) divided by (Pisano period of n^2). 4
1, 1, 1, 1, 1, 6, 1, 1, 1, 2, 1, 12, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 6, 1, 2, 1, 4, 1, 6, 1, 1, 1, 2, 1, 4, 1, 2, 1, 1, 1, 6, 1, 1, 1, 2, 1, 3, 1, 2, 3, 2, 1, 2, 1, 4, 3, 2, 1, 12, 1, 2, 1, 1, 1, 6, 1, 2, 3, 2, 1, 2, 1, 2, 1, 1, 1, 6, 1, 1, 1, 2, 1, 12, 1, 2, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Arpan Saha and C. S. Karthik, A few equivalences of Wall-Sun-Sun prime conjecture, arXiv:1102.1636 [math.NT], 2011.

Eric Weisstein's World of Mathematics, Pisano period.

Wikipedia, Pisano period.

FORMULA

a(n) = n/A237517(n).

MATHEMATICA

pp[1] = 1; pp[n_] := For[k = 1, True, k++, If[Mod[Fibonacci[k], n] == 0 && Mod[Fibonacci[k+1], n] == 1, Return[k]]];

a[n_] := n pp[n]/pp[n^2];

Array[a, 100] (* Jean-Fran├žois Alcover, Dec 06 2018 *)

PROG

(PARI) fibmod(n, m)=((Mod([1, 1; 1, 0], m))^n)[1, 2]

entry_p(p)=my(k=1, c=Mod(1, p), o); while(c, [o, c]=[c, c+o]; k++); k

entry(n)=if(n==1, return(1)); my(f=factor(n), v); v=vector(#f~, i, if(f[i, 1]>1e14, entry_p(f[i, 1]^f[i, 2]), entry_p(f[i, 1])*f[i, 1]^(f[i, 2] - 1))); if(f[1, 1]==2&&f[1, 2]>1, v[1]=3<<max(f[1, 2]-2, 1)); lcm(v)

per(n)=if(n==1, return(1)); my(k=entry(n)); forstep(i=k, n^2, k, if(fibmod(i-1, n)==1, return(i)))

a(n)=n*per(n)/per(n^2)

CROSSREFS

Cf. A237517, A001175, A001176.

Sequence in context: A323160 A323166 A007732 * A126795 A348929 A334491

Adjacent sequences:  A237832 A237833 A237834 * A237836 A237837 A237838

KEYWORD

nonn

AUTHOR

Charles R Greathouse IV, Feb 13 2014

STATUS

approved

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Last modified November 27 03:13 EST 2021. Contains 349344 sequences. (Running on oeis4.)