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A277708
a(n) = Least prime divisor of n with an odd exponent, or 1 if n is a perfect square.
3
1, 2, 3, 1, 5, 2, 7, 2, 1, 2, 11, 3, 13, 2, 3, 1, 17, 2, 19, 5, 3, 2, 23, 2, 1, 2, 3, 7, 29, 2, 31, 2, 3, 2, 5, 1, 37, 2, 3, 2, 41, 2, 43, 11, 5, 2, 47, 3, 1, 2, 3, 13, 53, 2, 5, 2, 3, 2, 59, 3, 61, 2, 7, 1, 5, 2, 67, 17, 3, 2, 71, 2, 73, 2, 3, 19, 7, 2, 79, 5, 1, 2, 83, 3, 5, 2, 3, 2, 89, 2, 7, 23, 3, 2, 5, 2, 97, 2, 11, 1, 101, 2, 103, 2, 3
OFFSET
1,2
LINKS
FORMULA
a(n) = A008578(1+A277707(n)).
a(n) = A020639(A007913(n)).
PROG
(Scheme, two different implementations)
(define (A277708 n) (A008578 (+ 1 (A277707 n))))
(define (A277708 n) (A020639 (A007913 n)))
(PARI) a(n) = my(f = factor(core(n))); if (!#f~, 1, vecmin(f[, 1])); \\ Michel Marcus, Oct 30 2016
(Python)
from sympy import primefactors
from sympy.ntheory.factor_ import core
def lpf(n): return 1 if n==1 else primefactors(n)[0]
def a(n): return lpf(core(n)) # Indranil Ghosh, May 17 2017
CROSSREFS
Cf. A000290 (after its initial zero-term gives the positions of ones in this sequence).
Cf. also A277698.
Sequence in context: A158584 A086112 A138798 * A360496 A356473 A328661
KEYWORD
nonn
AUTHOR
Antti Karttunen, Oct 28 2016
STATUS
approved