A388132 Triangular array read by rows: row n consists of the numbers k such that A075255(k) = A385964(n).

8, 1, 6, 20, 21, 26, 49, 52, 57, 74, 88, 91, 95, 111, 146, 810, 846, 851, 871, 995, 1191, 2117, 2147, 2159, 2359, 2692, 3027, 4034, 1280, 1302, 1333, 1349, 1397, 1477, 1684, 1893, 9430, 9563, 9577, 9593, 9703, 9899, 10307, 11705, 12484, 7739, 7747, 7783, 7807, 7859, 7999, 8203, 8327, 10084, 15122

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..231

Example

Row 3 is 20, 21, 26 because A385964(3) = 11 and the 3 numbers k such that A075255(k) = 11 are 20, 21, 26 (11 = 20 - 2*2 - 5 = 21 - 3 - 7 = 26 - 2 - 13).
The first 8 rows are
  8;
  1, 6;
  20, 21, 26;
  49, 52, 57, 74;
  88, 91, 95, 111, 146;
  810, 846, 851, 871, 995, 1191;
  2117, 2147, 2159, 2359, 2692, 3027, 4034;
  1280, 1302, 1333, 1349, 1397, 1477, 1684, 1893.

Maple

sopfr:= proc(n) local F, t;
  F:= ifactors(n)[2];
  add(t[1]*t[2], t=F)
end proc:
M:= 5*10^6: Mh:= M/2-2:
R:= map(t -> t - sopfr(t) , [$1..M]):
RS:= sort(select(t -> t > 0 and t <= Mh, R)):
V:= Array(1..21):
state:= 1: r:= RS[1]:
for i from 2 to nops(RS) do
  if RS[i] = r then
    state:= state+1
  else
    if V[state] = 0 then V[state]:= r fi;
    state:= 1: r:= RS[i]
  fi
od:
VL:=convert(V, list);
T:= Vector(22):
for i from 1 to M do
  if member(R[i], VL, 'k') then if T[k] = 0 then T[k]:= i else T[k]:= T[k], i fi fi
od:
for i from 1 to 21 do T[i] od;

Crossrefs

Cf. A075255, A385964.

Sequence in context: A240982 A258146 A182551 * A005486 A377513 A010157

Adjacent sequences: A388129 A388130 A388131 * A388133 A388134 A388135

Keyword

nonn,tabl

Author

Will Gosnell and Robert Israel, Sep 15 2025

Status

approved