login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Triangle in which row n contains the first n terms of A018805.
1

%I #23 May 24 2023 12:26:51

%S 1,1,3,1,3,7,1,3,7,11,1,3,7,11,19,1,3,7,11,19,23,1,3,7,11,19,23,35,1,

%T 3,7,11,19,23,35,43,1,3,7,11,19,23,35,43,55,1,3,7,11,19,23,35,43,55,

%U 63,1,3,7,11,19,23,35,43,55,63,83

%N Triangle in which row n contains the first n terms of A018805.

%C Sequence B is called a reluctant sequence of sequence A, if B is triangle array read by rows: row number k coincides with first k elements of the sequence A. Sequence A122507 is the reluctant sequence of A018805. - _Boris Putievskiy_, Dec 14 2012

%H Boris Putievskiy, <a href="http://arxiv.org/abs/1212.2732">Transformations Integer Sequences And Pairing Functions</a>, arXiv:1212.2732 [math.CO], 2012.

%F a(n) = A018805(m), where m = n-t(t+1)/2, t = floor((-1+sqrt(8*n-7))/2). - _Boris Putievskiy_, Dec 14 2012

%e 1

%e 1, 3

%e 1, 3, 7

%e 1, 3, 7, 11

%e 1, 3, 7, 11, 19

%e 1, 3, 7, 11, 19, 23

%t a1 = Table[ FoldList[ Plus, 1, 2 Array[ EulerPhi, n, 2 ] ], {n, 0, 10}] Flatten[a1]

%t Module[{nn=20,ep},ep=Accumulate[2*EulerPhi[Range[nn]]]-1;Table[Take[ep,n],{n,nn}]]// Flatten (* _Harvey P. Dale_, May 24 2023 *)

%Y Cf. A018805.

%K nonn,tabl

%O 1,3

%A _Roger L. Bagula_, Sep 15 2006

%E Edited by _N. J. A. Sloane_, Jun 16 2007