A070229 Next m>n such that m is divisible by lpf(n), lpf=A006530 largest prime factor.

2, 4, 6, 6, 10, 9, 14, 10, 12, 15, 22, 15, 26, 21, 20, 18, 34, 21, 38, 25, 28, 33, 46, 27, 30, 39, 30, 35, 58, 35, 62, 34, 44, 51, 42, 39, 74, 57, 52, 45, 82, 49, 86, 55, 50, 69, 94, 51, 56, 55, 68, 65, 106, 57, 66, 63, 76, 87, 118, 65, 122

Offset: 1

Author

Reinhard Zumkeller, May 07 2002

Keywords

• nonn
• easy

Comments

Or, for n>1, n + (largest prime divisor of n). [Anne Robinson, daughter of Herman P. Robinson, Oct 08 1981]

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• H. P. Robinson, Letter to N. J. A. Sloane, Oct 1981

Crossrefs

Cf. A036441.

Cf. A006530, A061228, A256393.

Iterations: A076271 (start=1), A036441 (start=2), A123581 (start=3).

Programs

Haskell

a070229 n = n + a006530 n
-- Reinhard Zumkeller, Nov 08 2015, Nov 14 2011

Mathematica

Table[n + Last@(First/@FactorInteger[n]), {n, 70}] (* Vladimir Joseph Stephan Orlovsky, Apr 08 2011 *)

PARI

vector(100, n, if(n>1, vecmax(factor(n)[, 1]), 1) + n) \\ Altug Alkan, Nov 13 2015

Formula

a(n) = (n/lpf(n)+1)*lpf(n).

a(n) = n+lpf(n) where lpf=A006530 largest prime factor. For example, a(14)=14+7=21 (instead of ((14/7)+1)*7). - Philippe Lallouet (philip.lallouet(AT)wanadoo.fr), Jun 14 2007