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A000095 Number of fixed points of GAMMA_0 (n) of type i. 2
1, 2, 0, 0, 2, 0, 0, 0, 0, 4, 0, 0, 2, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 2, 4, 0, 0, 2, 0, 0, 0, 0, 4, 0, 0, 2, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 2, 0, 0, 0, 0, 4, 0, 0, 2, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 2, 4, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 4, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 2, 0, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

B. Schoeneberg, Elliptic Modular Functions, Springer-Verlag, NY, 1974, p. 101.

G. Shimura, Introduction to the Arithmetic Theory of Automorphic Functions, Princeton, 1971, see p. 25, Eq. (2).

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

a(n) is multiplicative with a(2) = 2, a(2^e) = 0 if e>1, a(p^e) = 2 if p == 1 mod 4 and a(p^e) = 0 if p == 3 mod 4. - Michael Somos, Jul 15 2004

EXAMPLE

G.f. = x + 2*x^2 + 2*x^5 + 4*x^10 + 2*x^13 + 2*x^17 + 2*x^25 + 4*x^26 + 2*x^29 + ...

MAPLE

A000095 := proc(n) local b, d: if irem(n, 4) = 0 then RETURN(0); else b := 1; for d from 2 to n do if irem(n, d) = 0 and isprime(d) then b := b*(1+legendre(-1, d)); fi; od; RETURN(b); fi: end;

MATHEMATICA

A000095[ 1 ] = 1; A000095[ n_Integer ] := If[ Mod[ n, 4 ]==0, 0, Fold[ #1*(1+JacobiSymbol[ -1, #2 ])&, If[ EvenQ[ n ], 2, 1 ], Select[ First[ Transpose[ FactorInteger[ n ] ] ], OddQ ] ] ]

a[ n_] := If[ n < 1, 0, Times @@ (Which[# == 1, 1, # == 2, 2 Boole[#2 == 1], Mod[#, 4] == 1, 2, True, 0] & @@@ FactorInteger[n])]; (* Michael Somos, Nov 15 2015 *)

PROG

(PARI) {a(n) = my(t); if( n<=1 || n%4==0, n==1, t=1; fordiv(n, d, if( isprime(d), t *= (1 + kronecker(-1, d)))); t)}; /* Michael Somos, Jul 15 2004 */

(Haskell)

a000095 n = product $ zipWith f (a027748_row n) (a124010_row n) where

   f 2 e = if e == 1 then 2 else 0

   f p _ = if p `mod` 4 == 1 then 2 else 0

-- Reinhard Zumkeller, Mar 24 2012

(PARI) A000095(n)=n%3 && n%4 && n%7 && n%11 && return(prod(k=1, #n=factor(n)[, 1], 1+kronecker(-1, n[k]))) /* the n%4 is needed, the others only reduce execution time by 34% */ \\ M. F. Hasler, Mar 24 2012

CROSSREFS

Cf. A027748, A124010, A000089.

Sequence in context: A079205 A317641 A107497 * A258322 A258034 A243828

Adjacent sequences:  A000092 A000093 A000094 * A000096 A000097 A000098

KEYWORD

nonn,easy,mult

AUTHOR

N. J. A. Sloane

EXTENSIONS

Values a(1)-a(10^4) double checked by M. F. Hasler, Mar 24 2012

STATUS

approved

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Last modified September 25 01:17 EDT 2018. Contains 315360 sequences. (Running on oeis4.)