A385964 a(n) is the least number that occurs exactly n times in A075255.

4, 2, 1, 11, 35, 71, 791, 2015, 1259, 9359, 7559, 15590, 42839, 75599, 110159, 251999, 262079, 576575, 393119, 453599, 665279, 1713599

Offset

0,1

Links

Table of n, a(n) for n=0..21.

Example

a(3) = 11 because A075255(20) = A075255(21) = A075255(26) = 11, i.e. 11 = 20 - 2*2 - 5 = 21 - 3 - 7 = 26 - 2 - 13, and no number smaller than 11 works.

Maple

sopfr:= proc(n) local F, t;
  F:= ifactors(n)[2];
  add(t[1]*t[2], t=F)
end proc:
M:= 2*10^6: Mh:=M/2-2:
g:= proc(t) local v; v:= t - sopfr(t); if v > 0 and v < Mh then v fi end proc:
R:= sort(map(g, [$1..M])):
V:= Array(0..20):
V[0]:= 4:
state:= 1: r:= R[1]:
for i from 2 to nops(R) do
  if R[i] = r then
    state:= state+1
  else
    if state <= 20 and V[state] = 0 then V[state]:= r fi;
    state:= 1: r:= R[i]
  fi
od:
convert(V, list);

Crossrefs

Cf. A075255, A388132.

Sequence in context: A049429 A328647 A383019 * A183158 A174005 A152818

Adjacent sequences: A385961 A385962 A385963 * A385965 A385966 A385967

Keyword

nonn,more

Author

Will Gosnell and Robert Israel, Sep 14 2025

Status

approved