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A109886 Index of first occurrence of n in A109883, or -1 if n does not occur in A109883. 2
1, 2, 3, 30, 5, 9, 7, 50, 20, 42, 11, 36, 13, 6510, 27, 54, 17, 70620, 19, 25, 46, 66, 23, 168630, 124, 98, 58, 78, 29 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Sequence continues: a(30)=??, 31, 70, 112, 100, 57, 200, 37, 484, 55, 102, 41, 49, 43, a(44)=??, 94, 114, 47, 225, 1264, 252, 104, 294, 53, 780, 87, 71940, 118, 138, 59, 4290, 61, 1470, 85, 306, 134, a(66)=??, 67, 6300, 142, 288, 71, 324, 73, a(74)=??, 712, 174, 158, 2940, 79, a(80)=??, 166, 186, 83, 1344210, 405, 242, 115, 1590, 89, a(90)=??, 141, 196, 406, 540, 119, 2310, 97, 390, 202, 222, ..., . - Jason Earls and Robert G. Wilson v, Jul 12 2005

Smallest number N with perfect deficiency n, that is, the first number such that A109883(N)=n. - Walter Kehowski, Sep 13 2005

LINKS

Table of n, a(n) for n=0..28.

EXAMPLE

a(7) = 50: divisors of 50 are 1,2,5,10,25,50; 50 - (1 + 2 + 5 + 10 + 25) = 7 and 50 is the smallest such number.

MAPLE

with(numtheory); pdef := proc(n) local k, d, divd; d:=n; divd:=sort([op(divisors(n))]); for k in divd while d>=k do d:=d-k; od; end: PDL:=[]; for z from 1 to 1 do for pd from 0 to 60 do for n from 1 to 200000 do missed:=true; if pdef(n)=pd then PDL:=[op(PDL), n]; missed:=false; break fi od; if missed then PDL:=[op(PDL), -1] fi od od; PDL; # Walter Kehowski, Sep 13 2005

MATHEMATICA

subtract = If[ #1 < #2, Throw[ #1], #1 - #2]&; f[n_] := Catch @ Fold[subtract, n, Divisors @ n] (* Bobby R. Treat, (DrBob(AT)bigfoot.com), Jul 14 2005 *)

t = Table[0, {60}]; Do[ a = f[n]; If[a < 60 && t[[a + 1]] == 0, t[[a + 1]] = n], {n, 10^8}] (* Robert G. Wilson v, Jul 14 2005 *)

CROSSREFS

Cf. A064510, A109883, A109884.

Sequence in context: A078727 A270550 A076977 * A277811 A127615 A210417

Adjacent sequences:  A109883 A109884 A109885 * A109887 A109888 A109889

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Jul 11 2005

EXTENSIONS

Corrected and extended by Jason Earls, Jul 12 2005

More terms from Walter Kehowski, Sep 13 2005

STATUS

approved

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Last modified October 18 03:14 EDT 2018. Contains 316302 sequences. (Running on oeis4.)