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A243620 Prime numbers whose digital sum equals the number of bits in its binary expansion. No zeros allowed in the decimal expansion. 1

%I #15 May 09 2021 21:52:46

%S 2,13,23,233,251,523,541,613,631,811,1163,1181,1217,1361,1433,1451,

%T 1523,1613,1721,1811,4153,4243,4261,4423,4441,4513,4621,5233,5323,

%U 5413,5431,5521,6133,6151,6421,7213,7321,7411,8231,9221

%N Prime numbers whose digital sum equals the number of bits in its binary expansion. No zeros allowed in the decimal expansion.

%C Subsequence of A243619, which in turn is a subsequence of A243615.

%H Andreas Boe, <a href="/A243620/b243620.txt">Table of n, a(n) for n = 1..10000</a>

%e 613 -> 6+1+3=10, 613 = 1001100101_2 (10 bits), so 613 is a term.

%t Select[Prime[Range[1200]],DigitCount[#,10,0]==0&&IntegerLength[ #,2] == Total[ IntegerDigits[#]]&] (* _Harvey P. Dale_, Jan 12 2019 *)

%o (PARI) isok(n) = isprime(n) && (sumdigits(n) == #binary(n)) && (vecmin(digits(n)) != 0); \\ _Michel Marcus_, Jun 08 2014

%Y Cf. A243619 (same principle, but zeros allowed).

%Y Cf. A243615 (same principle, but covers all positive integers).

%K nonn,base

%O 1,1

%A _Andreas Boe_, Jun 07 2014

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Last modified April 25 03:15 EDT 2024. Contains 371964 sequences. (Running on oeis4.)