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.

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.

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