cp's OEIS Frontend

A131507 2n+1 appears n+1 times.

%I A131507 #38 Nov 05 2024 12:18:14
%S A131507 1,3,3,5,5,5,7,7,7,7,9,9,9,9,9,11,11,11,11,11,11,13,13,13,13,13,13,13,
%T A131507 15,15,15,15,15,15,15,15,17,17,17,17,17,17,17,17,17,19,19,19,19,19,19,
%U A131507 19,19,19,19,21,21,21,21,21,21,21,21,21,21,21,23,23,23,23,23,23,23,23,23,23,23,23
%N A131507 2n+1 appears n+1 times.
%C A131507 Sum of terms of row n is (n+1)*(2n+1) = A000384(n+1). - _Michel Marcus_, Feb 02 2014
%C A131507 Where records occur give A000217. - _Omar E. Pol_, Nov 05 2015
%H A131507 Reinhard Zumkeller, <a href="/A131507/b131507.txt">Rows n = 0..125 of triangle, flattened</a>
%F A131507 a(n) = 2*floor(sqrt(2n+1)+1/2) - 1. - _Ridouane Oudra_, Oct 20 2019
%e A131507 As a triangle, the sequence starts:
%e A131507 1;
%e A131507 3, 3;
%e A131507 5, 5, 5;
%e A131507 7, 7, 7, 7;
%e A131507 9, 9, 9, 9, 9;
%e A131507 ...
%p A131507 seq(2*floor(sqrt(2*n+1)+1/2)-1, n=0..70); # _Ridouane Oudra_, Oct 20 2019
%t A131507 Table[2 n + 1, {n, 0, 11}, {n + 1}] // Flatten (* _Michael De Vlieger_, Nov 05 2015 *)
%o A131507 (Haskell)
%o A131507 a131507 n k = a131507_tabl !! n !! k
%o A131507 a131507_row n = a131507_tabl !! n
%o A131507 a131507_tabl = zipWith ($) (map replicate [1..]) [1, 3 ..]
%o A131507 a131507_list = concat a131507_tabl
%o A131507 -- _Reinhard Zumkeller_, Jul 12 2014, Mar 18 2011
%o A131507 (Chipmunk BASIC v3.6.4(b8)) # http://www.nicholson.com/rhn/basic/
%o A131507 for n=1 to 23 step 2
%o A131507 for j=1 to n  step 2
%o A131507 print str$(n)+", ";
%o A131507 next j : next n : print
%o A131507 end
%o A131507 # _Jeremy Gardiner_, Feb 02 2014
%o A131507 (Python)
%o A131507 from math import isqrt
%o A131507 def A131507(n): return (k:=isqrt(m:=n+1<<1))+(m>k*(k+1))-1<<1|1 # _Chai Wah Wu_, Nov 04 2024
%Y A131507 Cf. A000217, A002024, A003056, A005408.
%Y A131507 Cf. A001650.
%K A131507 nonn,tabl
%O A131507 0,2
%A A131507 _Paul Curtz_, Aug 13 2007