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A225711 Composite squarefree numbers n such that p(i)+1 divides n-1, where p(i) are the prime factors of n. 5
385, 2737, 6061, 6721, 17641, 24769, 25201, 31521, 34561, 49105, 66385, 76609, 79401, 113221, 136081, 180481, 194833, 199801, 254881, 268801, 311905, 321937, 328321, 362881, 436645, 469201, 506521, 545905, 547561, 558145, 628705, 642505, 649153, 778261, 884305 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Paolo P. Lava, Table of n, a(n) for n = 1..150

EXAMPLE

Prime factors of 24769 are 17, 31 and 47. We have that (24769-1)/(17+1) = 1376, (24769-1)/(31+1) = 774 and (24769-1)/(47+1) = 516.

MAPLE

with(numtheory); A225711:=proc(i, j) local c, d, n, ok, p, t;

for n from 2 to i do if not isprime(n) then p:=ifactors(n)[2]; ok:=1;

for d from 1 to nops(p) do if p[d][2]>1 or p[d][1]=j then ok:=0; break; fi;

if  not type((n+j)/(p[d][1]-j), integer) then ok:=0; break; fi; od;

if ok=1 then print(n); fi; fi; od; end: A225711(10^9, -1);

MATHEMATICA

t = {}; n = 0; len = -2; While[len <= 262, n++; {p, e} = Transpose[FactorInteger[n]]; If[Length[p] > 1 && Union[e] == {1} && Union[Mod[n - 1, p + 1]] == {0}, AppendTo[t, n]; len = len + Length[IntegerDigits[n]] + 2]]; t (* T. D. Noe, May 17 2013 *)

CROSSREFS

Cf. A208728, A225702-A225710, A225712-A225720.

Sequence in context: A157354 A065110 A200525 * A204712 A237102 A264421

Adjacent sequences:  A225708 A225709 A225710 * A225712 A225713 A225714

KEYWORD

nonn

AUTHOR

Paolo P. Lava, May 13 2013

STATUS

approved

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Last modified October 26 18:30 EDT 2021. Contains 348268 sequences. (Running on oeis4.)