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A247396 Number of even numbers in classes of classification of the positive numbers defined in comment in A247395.

%I A247396 #33 Dec 23 2024 14:53:44
%S A247396 0,1,3,8,12,36,24,60,36,84,156,60,204,156,84,180,300,336,120,384,276,
%T A247396 144,456,324,516,744,396,204,420,216,444,1680,516,804,276,1440,300,
%U A247396 924,960,660,1020,1056,360,1860,384,780,396,2460,2604,900,456,924,1416,480
%N A247396 Number of even numbers in classes of classification of the positive numbers defined in comment in A247395.
%C A247396 In the classification every class contains no more than a finite number of numbers with a given least prime divisor.
%H A247396 Indranil Ghosh, <a href="/A247396/b247396.txt">Table of n, a(n) for n = 0..1000</a>
%H A247396 Vladimir Shevelev, <a href="https://web.archive.org/web/*/http://list.seqfan.eu/oldermail/seqfan/2014-September/013643.html">A classification of the positive integers over primes</a>
%F A247396 For n>=3, a(n) = (prime(n)^2 - prime(n-1)^2)/2.
%e A247396 a(6) = (prime(6)^2 - prime(5)^2)/2 = (13^2 - 11^2)/2 = 24. - _Indranil Ghosh_, Mar 08 2017
%p A247396 A247396:=n->(ithprime(n)^2 - ithprime(n-1)^2)/2: 0,1,3,seq(A247396(n), n=3..100); # _Wesley Ivan Hurt_, Apr 18 2017
%t A247396 a[0] = 0; a[1] = 1; a[2] = 3; a[n_] := (Prime[n]^2 - Prime[n - 1]^2) / 2; Table[a[n], {n, 0, 53}] (* _Indranil Ghosh_, Mar 08 2017 *)
%o A247396 (PARI) for(n=0, 53, print1(if(n>2, (prime(n)^2 - prime(n - 1)^2)/2, if(n<2, n, 3)),", ")) \\ _Indranil Ghosh_, Mar 08 2017
%Y A247396 Cf. A000040, A156759, A247393, A247394, A247395.
%K A247396 nonn
%O A247396 0,3
%A A247396 _Vladimir Shevelev_, Sep 16 2014
%E A247396 More terms from _Peter J. C. Moses_, Sep 17 2014