login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A271441 a(1) = 2; if gpf(a(n-1)) <= n-1 then a(n) = a(n-1) + a(gpf(a(n-1))), else a(n) = a(n-1) + 1, where gpf(m) is the greatest prime factor of m. 1
2, 3, 4, 7, 8, 11, 12, 16, 19, 20, 28, 40, 48, 52, 100, 108, 112, 124, 125, 133, 258, 259, 260, 308, 336, 348, 349, 350, 362, 363, 391, 651, 1042, 1043, 1044, 1406, 1407, 1408, 1436, 1437, 1438, 1439, 1440, 1448, 1449, 1709, 1710, 1835, 1836, 1948 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Choosing the initial value a(1) = 2 seems to produce the most irregular sequence.

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..10000

EXAMPLE

Since a(11) = 28, gpf(28) = 7 and a(7) = 12, then a(12) = 28 + 12 = 40.

MATHEMATICA

Nest[Append[#, (x = #[[-1]]) + If[(p = FactorInteger[x][[-1, 1]]) <= Length@#, #[[p]], 1]] &, {2}, 49] (* Ivan Neretin, Jan 27 2017 *)

PROG

(PARI) gpf(n) = if (n==1, 1, vecmax(factor(n)[, 1]));

lista(nn) = {va = vector(nn); print1(va[1] = 2, ", "); for (n=2, nn, if (gpf(va[n-1]) <= n-1, va[n] = va[n-1] + va[gpf(va[n-1])], va[n] = va[n-1]+1); print1(va[n], ", "); ); } \\ Michel Marcus, Apr 09 2016

CROSSREFS

Cf. A006530 (gpf).

Sequence in context: A026808 A240767 A284937 * A328421 A003508 A225229

Adjacent sequences:  A271438 A271439 A271440 * A271442 A271443 A271444

KEYWORD

nonn,hear

AUTHOR

Cody M. Haderlie, Apr 07 2016

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 13 17:54 EDT 2020. Contains 335689 sequences. (Running on oeis4.)