A340296 a(n) is the first number whose digit sequence can be partitioned into primes in exactly n ways.

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

Robert Israel, Table of n, a(n) for n = 1..93

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

Adjacent sequences: A340293 A340294 A340295 * A340297 A340298 A340299

Keyword

nonn,base

Author

J. M. Bergot and Robert Israel, Jan 14 2021

Status

approved