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A340296
a(n) is the first number whose digit sequence can be partitioned into primes in exactly n ways.
1
2, 23, 223, 373, 2237, 2337, 19373, 22337, 22373, 23773, 31373, 23373, 37337, 223737, 223773, 223373, 233137, 233373, 237337, 1137337, 1937337, 1373373, 2233733, 2233137, 373373, 2233373, 2337313, 2237337, 2237373, 2337353, 3733313, 2331373, 3137337, 3137373, 3373373, 2337373, 2337337, 2373373
OFFSET
1,1
LINKS
EXAMPLE
For n=4, a(4) = 373 can be partitioned into primes in four ways: 3|7|3, 3|73, 37|3 and 373.
MAPLE
f:= proc(n) option remember; local i, t;
if isprime(n) then t:= 1 else t:= 0 fi;
for i from 1 to ilog10(n) do
if isprime(n mod 10^i) then t:= t + procname(floor(n/10^i)) fi
od;
t
end proc:
f(0):= 0:
V:= Vector(38):
for n from 2 to 10^7 do
v:= f(n);
if v > 0 and v <= 38 and V[v] = 0 then V[v]:= n fi
od:
convert(V, list);
CROSSREFS
Sequence in context: A069590 A024028 A288820 * A242904 A068167 A030456
KEYWORD
nonn,base
AUTHOR
J. M. Bergot and Robert Israel, Jan 14 2021
STATUS
approved