OFFSET
1,1
COMMENTS
Subsequence of A006881.
a(1) = 34453 is the only number <= 5*10^6 that is a triangular number.
EXAMPLE
34453 = 131*263 which are distinct Honaker primes.
120191 = 263*457 which are distinct Honaker primes.
MAPLE
isA006881 := proc(n)
if numtheory[bigomega](n) =2 and A001221(n) = 2 then
true ;
else
false ;
end if;
end proc:
isA344780 := proc(n)
if isA006881(n) then
for p in ifactors(n)[2] do
if not isA033548(op(1, p)) then
return false;
end if;
end do:
true ;
else
false;
end if;
end proc:
for n from 1 do
if isA344780(n) then
printf("%d, \n", n);
end if;
end do: # R. J. Mathar, Jul 07 2021
MATHEMATICA
fHQ[n_] := Plus @@ IntegerDigits@n == Plus @@ IntegerDigits@PrimePi@n;
lst = {}; Do[If[Plus @@ Last /@ FactorInteger[n] == 2, a = Length[First /@ FactorInteger[n]]; If[a == 2, b = First /@ FactorInteger[n]; c = b[[1]]; d = b[[2]]; If[fHQ[c] && fHQ[d], AppendTo[lst, {n, c, d}]]]], {n, 2000000}]; lst
CROSSREFS
KEYWORD
nonn,base
AUTHOR
K. D. Bajpai, May 28 2021
STATUS
approved