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%I #11 Feb 03 2016 17:01:11
%S 0,0,1,1,1,2,3,3,3,4,4,5,6,6,6,7,7,8,8,8,9,9,9,10,11,12,12,12,13,14,
%T 14,14,15,15,16,16,17,17,17,18,18,19,19,20,21,21,21,21,21,22,23,23,24,
%U 24,25,25,26,26,27,28,28,29,29,29,30,31,31,32,32,33,34,34,34,35,35,35,36,37,38,39,39,40,40,41
%N a(n) = number of 4k+1 primes among first n primes; least monotonic left inverse of A080147.
%C a(n) = number of 4k+1 primes (A002144) among primes in range 2 .. A000040(n).
%H Antti Karttunen, <a href="/A267097/b267097.txt">Table of n, a(n) for n = 1..65537</a>
%F Other identities. For all n >= 1:
%F a(A080147(n)) = n.
%F a(n) + A267098(n) = n-1.
%o (Scheme, with _Antti Karttunen_'s IntSeq-library)
%o (define A267097 (LEFTINV-LEASTMONO 1 1 A080147))
%Y Cf. A000040, A002144, A080147, A267098.
%Y Cf. also A267101.
%K nonn
%O 1,6
%A _Antti Karttunen_, Feb 01 2016
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