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 A050519 Increments of arithmetic progression of at least 6 terms having the same value of phi in A050518. 3
 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, 360, 390, 420, 450, 480, 510, 540, 570, 600, 630, 660, 690, 720, 750, 780, 810, 840, 870, 900, 930, 960, 990, 1020, 1050, 1080, 1110, 1140, 1170, 1200, 1230, 1260, 1290, 1320, 1350, 1380, 1410, 1440, 1470 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The first 112 terms are successive multiples of 30, but this sequence does not coincide with A249674: a(113) = 210. See the Khovanova link and comments in A050518. The increments <= 1000 for terms of A050518 between 13413600 and 10^9 (see comment on A050518) are 720, 750, 780, 810, 840, 870, 900, 930, 960, 990, 210, 210, 420, 30, 420, 630, 630, 840, 60, 840, 90, 30, 30, 120, 150, 30, 18. - Mauro Fiorentini, Apr 12 2015 LINKS Robert Israel, Table of n, a(n) for n = 1..114 Tanya Khovanova, Non Recursions MAPLE N:= 10^7: # to get all terms <= N in A050518 with(numtheory): Res:= NULL: phis:= {seq(phi(i), i=2..N)}: for m in phis do S:= convert(invphi(m), set); if nops(S) < 6 then next fi; for d from 0 to 4 do Sd[d]:= select(t-> (t mod 5 = d), S, d); nd:= nops(Sd[d]); for i0 from 1 to nd-1 do s0:= Sd[d][i0]; if s0 > N then break fi; for i5 from i0+1 to nd do s5:= Sd[d][i5]; incr:= (s5 - s0)/5; if {s0+incr, s0+2*incr, s0+3*incr, s0+4*incr} subset S then Res:= Res, [s0, incr]; fi od od; od; od: sort([Res], (s, t)->s[1]

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Last modified August 8 10:02 EDT 2024. Contains 375019 sequences. (Running on oeis4.)