A056938 Concatenate all the prime divisors in previous term (with repetition), starting at 49.

49, 77, 711, 3379, 31109, 132393, 344131, 1731653, 71143523, 11115771019, 31135742029, 717261644891, 11193431873899, 116134799345907, 3204751189066719, 31068250396355573, 62161149980213343, 336906794442245927, 734615161567701999, 31318836286194043641

Offset

1,1

Comments

This sequence provides a record of the search for the home prime for 49.

This sequence has now been followed for 117 steps without a prime being reached (after which of course it would simply repeat).

Links

Patrick De Geest, Table of n, a(n) for n = 1..119

P. De Geest, Home Primes

Eric Weisstein's World of Mathematics, Home Prime

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, 49, 25]
(* Second program: *)
NestList[FromDigits@ Flatten@ Map[IntegerDigits, FactorInteger[#] /. {p_, e_} /; p >= 1 :> If[p == 1, 1, ConstantArray[p, e]]] &, 49, 16] (* Michael De Vlieger, Apr 27 2017 *)

Prog

(PARI) a=vector(35); a[1]=49; for(k=2, length(a), f=factor(a[k-1]); for(i=1, matsize(f)[1], l=10^ceil(log(f[i, 1])/log(10)); for(j=1, f[i, 2], a[k]=a[k]*l+f[i, 1]))) \\ M. F. Hasler, Mar 09 2007

Crossrefs

Cf. A006919, A037273, A037274, A037271, A238579.

Sequence in context: A103216 A036307 A294028 * A267986 A337759 A207638

Adjacent sequences: A056935 A056936 A056937 * A056939 A056940 A056941

Keyword

nonn,base

Author

Robert G. Wilson v, Sep 05 2000

Extensions

b-file updated by Max Alekseyev, Nov 28 2017

Status

approved