cp's OEIS Frontend

A213671 The odd part of n^2 - n + 2.

%I A213671 #28 Jul 31 2020 06:46:42
%S A213671 1,1,1,7,11,1,11,29,37,23,7,67,79,23,53,121,137,77,43,191,211,29,127,
%T A213671 277,301,163,11,379,407,109,233,497,529,281,149,631,667,11,371,781,
%U A213671 821,431,113,947,991,259,541,1129,1177,613,319,1327,1379,179
%N A213671 The odd part of n^2 - n + 2.
%C A213671 The first composite term s of this sequence which is not multiple of a prime term appeared before s is a(245) = 29891 = 71*421 - neither of 71, 421 are terms before a(245). - _Peter J. C. Moses_, Mar 03 2013
%C A213671 The probability that n points uniformly distributed in (or on) a sphere are in the same hemisphere is (n^2-n+2)/2^n, for which this is the numerator. - _Charles R Greathouse IV_, Sep 18 2013
%H A213671 Amiram Eldar, <a href="/A213671/b213671.txt">Table of n, a(n) for n = 1..10000</a>
%F A213671 a(n) = A000265(n^2-n+2). - _R. J. Mathar_, Mar 10 2013
%p A213671 A213671 := proc(n)
%p A213671         A000265(n^2-n+2) ;
%p A213671 end proc: # _R. J. Mathar_, Mar 10 2013
%t A213671 Table[k = n^2 - n + 2; k/2^IntegerExponent[k, 2], {n, 100}] (* _T. D. Noe_, Mar 16 2013 *)
%o A213671 (PARI) a(n)=n=n^2-n+2;n>>valuation(n,2) \\ _Charles R Greathouse IV_, Sep 18 2013
%Y A213671 Cf. A000265, A014206.
%K A213671 nonn,easy
%O A213671 1,4
%A A213671 _Vladimir Shevelev_, Mar 03 2013