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A077721 Primes which can be expressed as sum of distinct powers of 7. 10

%I #15 Sep 07 2018 03:51:46

%S 7,2801,17207,19559,120401,134513,134807,137201,840743,842759,842801,

%T 941249,943601,958007,958049,958343,960793,5782001,5784409,5899307,

%U 5899601,5899657,5901659,6591089,6607903,6706393,6708787,6722801,6722857,6723193

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

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

%H Robert Israel, <a href="/A077721/b077721.txt">Table of n, a(n) for n = 1..10000</a>

%p 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);

%t Select[Prime[Range[10^6]], Max[IntegerDigits[#, 7]]<=1 &] (* _Vincenzo Librandi_, Sep 07 2018 *)

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

%K nonn

%O 1,1

%A _Amarnath Murthy_, Nov 19 2002

%E More terms from _Sascha Kurz_, Jan 03 2003

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Last modified March 28 04:13 EDT 2024. Contains 371235 sequences. (Running on oeis4.)