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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A061394 Number of distinct prime factors of n-th least prime signature (A025487); also a(n)-th prime is largest prime factor of n-th least prime signature; also a(n)-th primorial number is largest primorial factor of n-th least product of primorial numbers. 12
 0, 1, 1, 2, 1, 2, 1, 2, 3, 1, 2, 2, 3, 1, 2, 2, 3, 1, 2, 3, 2, 4, 2, 3, 1, 2, 3, 2, 4, 2, 3, 1, 2, 3, 2, 4, 2, 3, 3, 1, 3, 2, 4, 2, 3, 2, 4, 2, 3, 3, 1, 3, 2, 5, 4, 2, 3, 2, 4, 2, 3, 3, 1, 3, 2, 5, 4, 2, 3, 3, 2, 4, 3, 4, 2, 3, 4, 3, 2, 1, 3, 2, 5, 4, 2, 3, 3, 2, 4, 3, 4, 2, 5, 3, 4, 3, 2, 1, 3, 2, 5, 4, 2, 3, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS A002110(a(n)) = A247451(n). - Reinhard Zumkeller, Sep 17 2014 Number of parts of the associated prime signature. - Álvar Ibeas, Nov 01 2014 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A061395(A025487(n)) = A001221(A025487(n)) = A051903(A181822(n)). A000040(a(n)) = A006530(A025487(n)). PROG (Haskell) import Data.List (elemIndex); import Data.Maybe (fromJust) a061394 = fromJust . (`elemIndex` a002110_list) . a247451 -- Reinhard Zumkeller, Sep 17 2014 (PARI) isA025487(n)=my(k=valuation(n, 2), t); n>>=k; forprime(p=3, default(primelimit), t=valuation(n, p); if(t>k, return(0), k=t); if(k, n/=p^k, return(n==1))) [omega(n) | n <- [1..1000], isA025487(n)] \\ Or, for older versions: apply(omega, select(isA025487, [1..1000])) \\ Charles R Greathouse IV, Nov 07 2014 CROSSREFS Cf. A002110, A247451, A006530, A061395, A025487, A000040, A051903. A001221 by prime signature. Sequence in context: A136109 A105265 A193360 * A248141 A220694 A136314 Adjacent sequences:  A061391 A061392 A061393 * A061395 A061396 A061397 KEYWORD nonn AUTHOR Henry Bottomley, Apr 30 2001 EXTENSIONS Offset updated by Matthew Vandermast, Nov 08 2008 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.

Last modified May 8 17:26 EDT 2021. Contains 343666 sequences. (Running on oeis4.)