A085648 Brilliant numbers (A078972) whose digital sum is also brilliant.

4, 6, 9, 15, 121, 253, 361, 437, 451, 473, 527, 671, 703, 799, 851, 901, 923, 979, 1003, 1027, 1067, 1081, 1139, 1157, 1207, 1247, 1261, 1333, 1513, 1517, 1643, 1711, 2183, 2291, 2701, 2813, 3007, 3403, 3551, 3589, 3713, 4307, 4399, 4489, 5041, 5063, 5767

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

7470269 is a term because 7470269 = 1249*5981 and 7+4+7+0+2+6+9 = 35 = 5*7.

Maple

isbril:= proc(n) local F;
  F:= ifactors(n)[2];
  (nops(F)=1 and F[1][2]=2) or (nops(F)=2 and F[1][2]=1 and F[2][2]=1 and ilog10(F[1][1])=ilog10(F[2][1]))
end proc:
R:= NULL:
for d from 1 to 2 do
  if d = 1 then P:= [2, 3, 5, 7]
  else P:= select(isprime, [seq(i, i=10^(d-1)+1..10^d-1, 2)])
  fi;
  R:= R, op(sort(select(t -> isbril(convert(convert(t, base, 10), `+`)), [seq(seq(P[i]*P[j], j=1..i), i=1..nops(P))])))
od:
R; # Robert Israel, Nov 24 2020

Crossrefs

Cf. A078972.

Sequence in context: A136358 A115665 A118694 * A300131 A045114 A010436

Adjacent sequences: A085645 A085646 A085647 * A085649 A085650 A085651

Keyword

base,nonn

Author

Amarnath Murthy, Jason Earls, Jul 11 2003

Extensions

Offset changed by Robert Israel, Nov 24 2020

Status

approved