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Numbers of the form 2k - 1 such that A246702(k) = 3.
1

%I #27 May 15 2020 02:26:03

%S 15,33,43,45,69,75,87,99,109,135,141,157,159,177,207,213,225,229,249,

%T 261,277,283,297,303,307,321,363,375,393,405,423,447,477,499,501,519,

%U 531,537,573,591,621,639,643,675,681,691,717,733,739,747,783,789,807,811

%N Numbers of the form 2k - 1 such that A246702(k) = 3.

%C Composites in this sequence: 15, 33, 45, 69, 75, 87, 99, 135, 141, 159, 177, 207, 213, 225, 249, 261, 297, 303, 321, 363, 375, 393, 405, 423, 447, 477, ...

%e A246702(8) = 3 for the first time, hence a(1) = 2*8 - 1 = 15.

%o (PARI) is(k) = (m=Mod(k%2, k*k)) && sum(i=1, k*k-1, m*=2; m==1) == 3; \\ _Jinyuan Wang_, May 15 2020

%Y Cf. Numbers of the form 2k - 1 such that A246702(k) = m: number 1 (m = 0), A167791 (m = 1), A246717 (m = 2), this sequence (m = 3), A001133 (primes in this sequence).

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Nov 15 2014

%E More terms from and terms corrected by _Jinyuan Wang_, May 15 2020