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A051904 Minimal exponent in prime factorization of n. 29
0, 1, 1, 2, 1, 1, 1, 3, 2, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 3, 1, 1, 1, 1, 5, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 6, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Daniel Forgues, Table of n, a(n) for n = 1..100000

Eric Weisstein's World of Mathematics, Niven's Constant

Index entries for sequences computed from exponents in factorization of n

FORMULA

a(n) = min(k=1..A001221(n), A124010(n,k) ). - Reinhard Zumkeller, Aug 27 2011

a(1) = 0, for n > 1, if A001221(n) = 1 (when n is in A000961), a(n) = A001222(n), otherwise a(n) = min(A067029(n), a(A028234(n))). - Antti Karttunen, Jul 12 2017

EXAMPLE

For n = 72 = 2^3*3^2, a(72) = min(exponents) = min(3,2) = 2.

MAPLE

a := proc (n) if n = 1 then 0 else min(seq(op(2, op(j, op(2, ifactors(n)))), j = 1 .. nops(op(2, ifactors(n))))) end if end proc: seq(a(n), n = 1 .. 100); # Emeric Deutsch, May 20 2015

MATHEMATICA

Table[If[n == 1, 0, Min @@ Last /@ FactorInteger[n]], {n, 100}] (* Ray Chandler, Jan 24 2006 *)

PROG

(Haskell)

a051904 1 = 0

a051904 n = minimum $ a124010_row n  -- Reinhard Zumkeller, Jul 15 2012

(PARI) a(n)=vecmin(factor(n)[, 2]) \\ Charles R Greathouse IV, Nov 19 2012

(Scheme) (define (A051904 n) (cond ((= 1 n) 0) ((= 1 (A001221 n)) (A001222 n)) (else (min (A067029 n) (A051904 (A028234 n)))))) ;; Antti Karttunen, Jul 12 2017

(Python)

from sympy import factorint

def a(n):

    f=factorint(n)

    l=[f[p] for p in f]

    return 0 if n==1 else min(l)

print map(a, xrange(1, 151)) # Indranil Ghosh, Jul 13 2017

CROSSREFS

Cf. A000961, A001221, A005361, A008479, A051903, A052409, A076558, A124010.

Sequence in context: A253641 A158378 A052409 * A070012 A071178 A072776

Adjacent sequences:  A051901 A051902 A051903 * A051905 A051906 A051907

KEYWORD

nonn,easy

AUTHOR

Labos Elemer, Dec 16 1999

STATUS

approved

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Last modified December 13 00:17 EST 2017. Contains 295954 sequences.