OFFSET
1,3
REFERENCES
J. Neukirch, Class Field Theory, Springer, p. 1.
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
EXAMPLE
24=3*2^3, 1=3*3-1*2^3, a(24)=3*3=9.
MATHEMATICA
a[1] = a[2] = 1; a[n_?OddQ] := n; a[n_] := (s = IntegerExponent[n, 2]; r = n/2^s; eq = Reduce[1 == t*r + u*2^s, {t, u}, Integers] /. C[_] -> 0; t*r /. Solve[eq] // First ); Table[a[n], {n, 1, 76}] (* Jean-François Alcover, Jun 07 2013 *)
PROG
(C) for(n=1; n<=100; n++) { r=n; s=1; while((r&1)==0) { r>>=1; s<<=1; } for(t=1; t<9999; t++) { if(((t*r-1)%s)==0) { printf("%d, ", t*r); break; } if(((t*r+1)%s)==0) { printf("%d, ", -t*r); break; } } if((n%10)==0) printf("\n"); if(t==9999) exit(0); //"not found": error }
(Haskell)
a040026 n = f 1 where
f t | (1 - t*r) `mod` s == 0 = t*r
| (1 + t*r) `mod` s == 0 = - t*r
| otherwise = f (t + 1)
(r, s) = split n 1
split x y | m == 0 = split x' (2 * y)
| m == 1 = (x, y) where (x', m) = divMod x 2
-- Reinhard Zumkeller, Jul 21 2012
CROSSREFS
KEYWORD
AUTHOR
EXTENSIONS
More terms from Arlin Anderson (starship1(AT)gmail.com)
STATUS
approved