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 A122507 Triangular in which row n contains first n terms of A018805. 1
 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 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 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 LINKS Boris Putievskiy, Transformations Integer Sequences And Pairing Functions arXiv:1212.2732 [math.CO] 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 EXAMPLE 1 1, 3 1, 3, 7 1, 3, 7, 11 1, 3, 7, 11, 19 1, 3, 7, 11, 19, 23 MATHEMATICA a1 = Table[ FoldList[ Plus, 1, 2 Array[ EulerPhi, n, 2 ] ], {n, 0, 10}] Flatten[a1] CROSSREFS Cf. A018805. Sequence in context: A205121 A152903 A226522 * A257258 A259325 A094250 Adjacent sequences:  A122504 A122505 A122506 * A122508 A122509 A122510 KEYWORD nonn,tabl AUTHOR Roger L. Bagula, Sep 15 2006 EXTENSIONS Edited by N. J. A. Sloane, Jun 16 2007 STATUS approved

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Last modified May 31 19:40 EDT 2020. Contains 334748 sequences. (Running on oeis4.)