A122507 Triangle in which row n contains the first n terms of A018805.

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

Offset: 1

Author

Roger L. Bagula, Sep 15 2006

Keywords

• nonn
• tabl

Comments

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

Examples

			1
1, 3
1, 3, 7
1, 3, 7, 11
1, 3, 7, 11, 19
1, 3, 7, 11, 19, 23
		

Links

• Boris Putievskiy, Transformations Integer Sequences And Pairing Functions, arXiv:1212.2732 [math.CO], 2012.

Crossrefs

Cf. A018805.

Programs

Mathematica

a1 = Table[ FoldList[ Plus, 1, 2 Array[ EulerPhi, n, 2 ] ], {n, 0, 10}] Flatten[a1]
Module[{nn=20,ep},ep=Accumulate[2*EulerPhi[Range[nn]]]-1;Table[Take[ep,n],{n,nn}]]// Flatten (* Harvey P. Dale, May 24 2023 *)

Formula

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

Extensions

Edited by N. J. A. Sloane, Jun 16 2007