|
%I #6 Oct 23 2020 15:56:17
%S 1,1,2,2,1,1,2,3,3,3,2,1,1,2,3,4,4,4,4,3,2,1,1,2,3,4,5,5,5,5,5,4,3,2,
%T 1,1,2,3,4,5,6,6,6,6,6,6,5,4,3,2,1,1,2,3,4,5,6,7,7,7,7,7,7,7,6,5,4,3,
%U 2,1,1,2,3,4,5,6,7,8,8,8,8,8,8,8,8,7
%N Crescendo trapezoidal.
%C a(A000326(n)) = a(A143689(n-1)) = 1;
%C for all n: a(k) = n, A104249(n-1) <= k <= A005448(n).
%H Reinhard Zumkeller, <a href="/A242357/b242357.txt">Table of n, a(n) for n = 1..1001</a>
%e . Initial values
%e . seen trapezoidal: 666666
%e . 55555 5......5
%e . 4444 4.....4 4........4
%e . 333 3....3 3.......3 3..........3
%e . 22 2...2 2......2 2.........2 2............2
%e . 1 1..1 1.....1 1........1 1...........1 1..............1 .
%t Table[Join[Range[n-1],PadRight[{},n,n],Range[n-1,1,-1]],{n,9}]//Flatten (* _Harvey P. Dale_, Oct 23 2020 *)
%o (Haskell)
%o import Data.List (inits)
%o a242357 n = a242357_list !! (n-1)
%o a242357_list = concatMap f $ tail $ inits [1..] where
%o f us = (init us) ++ (take v [v, v ..]) ++ vs
%o where (v:vs) = reverse us
%Y Cf. A004737.
%K nonn
%O 1,3
%A _Reinhard Zumkeller_, May 11 2014
|
