A322982 If n is a noncomposite, then a(n) = 2*n - 1, otherwise a(n) = A032742(n), the largest proper divisor of n.

1, 3, 5, 2, 9, 3, 13, 4, 3, 5, 21, 6, 25, 7, 5, 8, 33, 9, 37, 10, 7, 11, 45, 12, 5, 13, 9, 14, 57, 15, 61, 16, 11, 17, 7, 18, 73, 19, 13, 20, 81, 21, 85, 22, 15, 23, 93, 24, 7, 25, 17, 26, 105, 27, 11, 28, 19, 29, 117, 30, 121, 31, 21, 32, 13, 33, 133, 34, 23, 35, 141, 36, 145, 37, 25, 38, 11, 39, 157, 40, 27, 41, 165, 42, 17, 43, 29

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..20000

Formula

If A010051(n) == 1, a(n) = 2*n - 1, otherwise a(n) = A032742(n) = n/A020639(n).

Mathematica

Array[If[CompositeQ@ #, Divisors[#][[-2]], 2 # - 1] &, 87] (* Michael De Vlieger, Jan 03 2019 *)

Prog

(PARI) A322982(n) = if((1==n)||isprime(n), n+n-1, n/vecmin(factor(n)[, 1]));

Crossrefs

Cf. A010051, A020639, A032742, A087717.

Sequence in context: A152649 A327263 A186412 * A275846 A273668 A356472

Adjacent sequences: A322979 A322980 A322981 * A322983 A322984 A322985

Keyword

nonn

Author

Antti Karttunen, Jan 03 2019

Status

approved