A109884 - OEIS

A109884

Indices k of members of A109883 such that A109883(k) is a divisor of k. Also k is a term if A109883(k) = 0.

1, 2, 4, 6, 8, 10, 12, 16, 18, 24, 28, 30, 32, 40, 44, 48, 60, 64, 72, 84, 120, 126, 128, 136, 140, 150, 152, 180, 184, 204, 216, 224, 234, 256, 270, 360, 420, 440, 462, 468, 496, 512, 520, 528, 546, 672, 700, 750, 752, 864, 870, 884

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OFFSET

1,2

COMMENTS

2^n is a term for all n. All perfect numbers are terms.

LINKS

Nathaniel Johnston, Table of n, a(n) for n = 1..463

EXAMPLE

18 is a term as A109883(18) = 6, 6 is a divisor of 18.

6 is a term as A109883(6) = 0.

MAPLE

for n from 1 to 900 do if(A109883(n)=0 or type(n/A109883(n), integer))then print(n); fi:od: # Nathaniel Johnston, Apr 15 2011

MATHEMATICA

With[{s = Table[Catch@ Fold[If[#1 < #2, Throw[#1], #1 - #2] &, n, Divisors@ n], {n, 10^3}]}, Select[MapIndexed[{First@ #2, #1 /. 0 -> 1} &, s], Divisible[#1, #2] & @@ # &][[All, 1]]] (* Michael De Vlieger, Aug 17 2017, after Bobby R. Treat at A109883 *)

CROSSREFS

Cf. A064510, A109883.

Sequence in context: A090778 A097380 A114270 * A015926 A085154 A371286

Adjacent sequences: A109881 A109882 A109883 * A109885 A109886 A109887

KEYWORD

easy,nonn

AUTHOR

Amarnath Murthy, Jul 11 2005

EXTENSIONS

Offset, a(11), and a(12) corrected by, and a(13) - a(52) from Nathaniel Johnston, Apr 15 2011

STATUS

approved