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%I #20 Oct 08 2021 14:45:26
%S 1,3,5,7,11,13,17,19,23,27,31,33,39,41,45,49,55,57,63,65,71,75,79,81,
%T 89,93,97,101,107,109,117,119,125,129,133,137,147,149,153,157,165,167,
%U 175,177,183,189,193,195,205,209,215,219,225,227,235,239,247,251,255,257,269
%N a(n) = 1 + floor(sqrt(n)) + Sum_{i=1..n} floor(n/i).
%C Matches first 8 odd primes.
%H Antti Karttunen, <a href="/A132106/b132106.txt">Table of n, a(n) for n = 0..16384</a>
%F a(n) = 1 + Sum_{i=1..n} A161841(i) for n > 0. - _Christian Krause_, Jun 17 2021
%F a(n) = 1 + A000196(n) + A006218(n). - _Vaclav Kotesovec_, Jul 01 2021
%o (PARI) a(n) = 1 + sqrtint(n) + sum(i=1, n, n\i); \\ _Michel Marcus_, Jun 17 2021
%o (Python)
%o from math import isqrt
%o def A132106(n): return (lambda m: 2*(sum(n//k for k in range(1, m+1)))+m*(1-m)+1)(isqrt(n)) # _Chai Wah Wu_, Oct 08 2021
%Y Cf. A000196, A006218, A161841 (first differences).
%K nonn
%O 0,2
%A Richard C. Schroeppel, Oct 31 2007
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