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Write down all the prime divisors in previous term.
(Formerly M4581)
5

%I M4581 #21 Oct 07 2022 15:47:24

%S 8,222,2337,31941,33371313,311123771,7149317941,22931219729,

%T 112084656339,3347911118189,11613496501723,97130517917327,

%U 531832651281459,3331113965338635107,3331113965338635107

%N Write down all the prime divisors in previous term.

%D H. Jaleebi, personal communication.

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

%H Patrick De Geest, <a href="http://www.worldofnumbers.com/topic1.htm">Home Primes</a>

%F a(n+1) = A037276(a(n)), a(1) = 8. - _M. F. Hasler_, Oct 07 2022

%t 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 ]

%t NestList[FromDigits[Flatten[IntegerDigits/@(Table[First[#],{Last[#]}]& /@ FactorInteger[#])]]&,8,15] (* _Harvey P. Dale_, Dec 04 2011 *)

%o (PARI) first(N, a=8)=vector(N,i,if(i>1,a=A037276(a),a)) \\ _M. F. Hasler_, Oct 07 2022

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

%K nonn,base,nice

%O 1,1

%A _N. J. A. Sloane_

%E More terms from _Robert G. Wilson v_, Sep 05 2000, who remarks that sequence stabilizes at 13th term with a prime.