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A114751 The following triangle contains n consecutive numbers beginning from n in ascending order if n is odd else in descending order. Sequence contains the triangle by rows. 2

%I #19 Aug 19 2019 04:02:00

%S 1,3,2,3,4,5,7,6,5,4,5,6,7,8,9,11,10,9,8,7,6,7,8,9,10,11,12,13,15,14,

%T 13,12,11,10,9,8,9,10,11,12,13,14,15,16,17,19,18,17,16,15,14,13,12,11,

%U 10,11,12,13,14,15,16,17,18,19,20,21,23,22,21,20,19,18,17,16,15,14,13,12

%N The following triangle contains n consecutive numbers beginning from n in ascending order if n is odd else in descending order. Sequence contains the triangle by rows.

%F a(n) = (3*t+2-t*(-1)^(t-1))/2-(1+(-1)^t)*(j-1)/2+(1-(-1)^t)*(j-1)/2, where j = (t*t+3*t+4)/2-n, t=floor((-1+sqrt(8*n-7))/2). - _Boris Putievskiy_, Jan 30 2013

%e 1

%e 3 2

%e 3 4 5

%e 7 6 5 4

%e 5 6 7 8 9

%e 11 10 9 8 7 6

%e ...

%p for n from 1 to 14 do if n mod 2 = 1 then print(seq(k,k=n..2*n-1)) else print(seq(2*n-k,k=1..n)) fi od; # yields sequence in triangular form # _Emeric Deutsch_, Jan 26 2006

%Y Cf. A114752, A114753, A210530.

%K easy,nonn,tabl

%O 1,2

%A _Amarnath Murthy_, Nov 15 2005

%E More terms from _Emeric Deutsch_, Jan 26 2006

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)