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A344032
a(n) is the least prime that begins a sequence of at least n distinct primes under iteration of A061762.
1
2, 11, 23, 53, 12451, 36779999
OFFSET
1,1
EXAMPLE
12451 is prime and A061762(12451) = 1*2*4*5*1+1+2+4+5+1 = 53.
53 is prime and A061762(53) = 5*3+5+3 = 23.
23 is prime and A061762(23) = 2*3+2+3 = 11.
11 is prime and A061762(11) = 1*1+1+1 = 3.
3 is prime and A061762(3) = 3+3 = 6 is not prime.
Thus 12451 begins a sequence of 5 distinct primes under the iteration of A061762. Since 12451 is the least such prime, a(5) = 12451.
MAPLE
f:= proc(n) local L;
L:= convert(n, base, 10);
convert(L, `+`)+convert(L, `*`)
end proc:
g:= proc(n) local S, v;
S:= {n}:
v:= n;
do
v:= f(v);
if member(v, S) or not isprime(v) then return nops(S) fi;
S:= S union {v}
od
end proc:
R:= NULL: p:= 1: m:= 0:
while m < 5 do
p:= nextprime(p);
v:= g(p);
if v > m then R:= R, p$(v-m); m:= v fi
od:
R;
CROSSREFS
Sequence in context: A090424 A056637 A141423 * A338225 A106974 A198277
KEYWORD
nonn,base,more
AUTHOR
J. M. Bergot and Robert Israel, May 07 2021
STATUS
approved