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Search: id:A076426
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| A076426 |
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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. |
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+0
3
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OFFSET
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0,1
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COMMENT
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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.
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FORMULA
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abs(reverse(lpd(n))-reverse(Lpf(n))) = n.
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EXAMPLE
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lpd(5750) = 2875; Lpf(5750) = 23; 5782 - 32 = 5750.
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PROGRAM
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(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, ", ")))}
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CROSSREFS
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Cf. A076423, A076425.
Sequence in context: A028547 A043484 A069301 this_sequence A055354 A053862 A096399
Adjacent sequences: A076423 A076424 A076425 this_sequence A076427 A076428 A076429
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KEYWORD
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base,more,nonn
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AUTHOR
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Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Oct 11 2002
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