A077721 Primes which can be expressed as sum of distinct powers of 7.

7, 2801, 17207, 19559, 120401, 134513, 134807, 137201, 840743, 842759, 842801, 941249, 943601, 958007, 958049, 958343, 960793, 5782001, 5784409, 5899307, 5899601, 5899657, 5901659, 6591089, 6607903, 6706393, 6708787, 6722801, 6722857, 6723193

Offset: 1

Author

Amarnath Murthy, Nov 19 2002

Keywords

• nonn

Comments

Primes whose base 7 representation contains only zeros and 1's.

Links

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

Crossrefs

Cf. A020449, A000695, A033044, A077717, A077718, A077719, A077720, A077722, A077723.

Programs

Maple

pos := 0:for i from 1 to 4000 do b := convert(i,base,2); s := sum(b[j]*7^(j-1),j=1..nops(b)): if(isprime(s)) then pos := pos+1:a[pos] := s:fi: od:seq(a[j],j=1..pos);

Mathematica

Select[Prime[Range[10^6]], Max[IntegerDigits[#, 7]]<=1 &] (* Vincenzo Librandi, Sep 07 2018 *)

Extensions

More terms from Sascha Kurz, Jan 03 2003