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 A231969 a(n) = the smallest squarefree number (A005117) with n prime factors in a 2p+1 progression. 4

%I #4 Nov 18 2013 16:39:40

%S 2,10,110,2530,118910,17036047229140531,

%T 4713753689937227789548410467592773787730621935419,

%U 4754361703029497628070972207349674154455369685904736544199583856401,17434718204270642890620908753958444038404912529730635812020757976125828120134034469

%N a(n) = the smallest squarefree number (A005117) with n prime factors in a 2p+1 progression.

%C Smallest squarefree numbers with n >= 2 prime divisors of the form p_1 * p_2 * … * p_n, where p_1 < p_2 < … < p_k = primes with p_k = 2 * p_(k-1) + 1.

%H Jaroslav Krizek, <a href="/A231969/b231969.txt">Table of n, a(n) for n = 1..12</a>

%e 17036047229140531 = 89*179*359*719*1439*2879, where 179 = 2*89 + 1, 359 = 2*179 + 1, 719 = 2*359 + 1, 1439 = 2*719 + 1, 2879 = 2*1439 + 1.

%Y Cf. A005117, A000040, A231966, A231967, A231968.

%K nonn

%O 1,1

%A _Jaroslav Krizek_, Nov 16 2013

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Last modified June 6 16:27 EDT 2023. Contains 363148 sequences. (Running on oeis4.)