A006919 Write down all the prime divisors in previous term. (Formerly M4581)

8, 222, 2337, 31941, 33371313, 311123771, 7149317941, 22931219729, 112084656339, 3347911118189, 11613496501723, 97130517917327, 531832651281459, 3331113965338635107, 3331113965338635107

Offset

1,1

References

H. Jaleebi, personal communication.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Table of n, a(n) for n=1..15.

Patrick De Geest, Home Primes

Formula

a(n+1) = A037276(a(n)), a(1) = 8. - M. F. Hasler, Oct 07 2022

Mathematica

g[ n_ ] := (x = n; d = {}; While[ FactorInteger[ x ] != {}, f = FactorInteger[ x, FactorComplete -> True ][ [ 1, 1 ] ]; x = x/f; AppendTo[ d, IntegerDigits[ f ] ] ]; FromDigits[ Flatten[ d ] ]); NestList[ g, 8, 15 ]
NestList[FromDigits[Flatten[IntegerDigits/@(Table[First[#], {Last[#]}]& /@ FactorInteger[#])]]&, 8, 15] (* Harvey P. Dale, Dec 04 2011 *)

Prog

(PARI) first(N, a=8)=vector(N, i, if(i>1, a=A037276(a), a)) \\ M. F. Hasler, Oct 07 2022

Crossrefs

Cf. A056938 (same for a(1)=49), A037271-A037276, A048985, A048986, A049065.

Sequence in context: A183261 A316954 A299734 * A179122 A300349 A300434

Adjacent sequences: A006916 A006917 A006918 * A006920 A006921 A006922

Keyword

nonn,base,nice

Author

N. J. A. Sloane

Extensions

More terms from Robert G. Wilson v, Sep 05 2000, who remarks that sequence stabilizes at 13th term with a prime.

Status

approved