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A076426 Fixed points of the mapping k -> abs(reverse(lpd(k))-reverse(Lpf(k))). lpd(k) is the largest proper divisor and Lpf(k) is the largest prime factor of k. 2
5750, 33866, 74841, 517250, 577750, 5538710, 51414250, 51454250, 51687250, 51727250, 51748250, 51858250, 52525250, 57515750, 57535750, 57575750, 57757750, 67597352, 841794296, 5120202250, 5120802250, 5121612250 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Besides these fixed points (cycles of length 1) there are five cycles of length 2 ([9378, 9739], [518775, 522075], [5170250, 5197250], [5219475, 5249775], [5255750, 5755250]) and one cycle of length 3 ([7285, 7467, 9711]) below 8000000.

LINKS

Table of n, a(n) for n=1..22.

FORMULA

abs(reverse(lpd(n))-reverse(Lpf(n))) = n.

EXAMPLE

lpd(5750) = 2875; Lpf(5750) = 23; 5782 - 32 = 5750.

PROG

(PARI) {for(n=1, 34000, v=divisors(n); a=matsize(v)[2]; z=if(a>1, v[a-1], 1); p=0; while(z>0, d=divrem(z, 10); z=d[1]; p=10*p+d[2]); z=if(n==1, 1, vecmax(component(factor(n), 1))); q=0; while(z>0, d=divrem(z, 10); z=d[1]; q=10*q+d[2]); if(abs(p-q)==n, print1(n, ", ")))}

CROSSREFS

Cf. A076423, A076425.

Sequence in context: A069301 A218048 A202419 * A251872 A190466 A157988

Adjacent sequences:  A076423 A076424 A076425 * A076427 A076428 A076429

KEYWORD

base,nonn

AUTHOR

Klaus Brockhaus, Oct 11 2002

EXTENSIONS

Offset corrected and a(7)-a(22) from Donovan Johnson, Aug 09 2010

STATUS

approved

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Last modified October 20 20:24 EDT 2019. Contains 328273 sequences. (Running on oeis4.)