A340641 a(n) is the least root of A340640(n).

2, 3, 5, 3, 2, 6, 7, 2, 3, 10, 11, 5, 2, 12, 14, 15, 3, 2, 17, 18, 19, 22, 23, 24, 26, 28, 31, 10, 2, 33, 35, 6, 11, 37, 41, 42, 45, 46, 3, 13, 47, 48, 50, 52, 53, 55, 56, 58, 59, 63, 65, 70, 71, 76, 77, 80, 82, 83, 88, 89, 90, 91, 96, 97, 99, 101, 103, 104, 110

Offset

1,1

Links

Table of n, a(n) for n=1..69.

Formula

a(n) = A025478(A340640(n)).

Example

a(1) = 2: A340640(1) = 4 = 2^2;
a(2) = 3: A340640(2) = 9 = 3^2;
a(3) = 5: A350640(3) = 25 = 5^2;
a(4) = 3: A340640(4) = 27 = 3^3.

Prog

(PARI) a340641(limit)={my(p2=999, p1=2, n2=1, n1=4); for(n=5, limit, my(p0=ispower(n)); if(p0>1, if(p2+p0>4, print1(round(n1^(1/p1)), ", ")); n2=n1; n1=n; p2=p1; p1=p0))};
a340641(13000)

Crossrefs

Cf. A025478, A340587, A340640.

Sequence in context: A197032 A321781 A254862 * A322235 A346477 A337583

Adjacent sequences: A340638 A340639 A340640 * A340642 A340643 A340644

Keyword

nonn

Author

Hugo Pfoertner, Jan 14 2021

Status

approved