login
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
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.
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
Sequence in context: A069301 A218048 A202419 * A251872 A190466 A157988
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