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A225704 Composite squarefree numbers n such that p(i)-4 divides n+4, where p(i) are the prime factors of n. 3
6, 10, 14, 15, 30, 35, 66, 266, 455, 806, 4154, 4686, 6665, 10370, 16646, 22781, 31146, 36305, 72086, 205871, 246506, 473711, 570011, 653666, 733586, 900581, 904046, 1422410, 1941971, 1969565, 2023010, 2807255, 2821269, 3009821, 3043274, 3355271, 3880301 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..37.

EXAMPLE

Prime factors of 205871 are 29, 31 and 229. We have that (205871+4)/(29-4) = 8235, (205871+4)/(31-4) = 7625 and (205871+4)/(229-4) = 915.

MAPLE

with(numtheory); A225704:=proc(i, j) local c, d, n, ok, p, t;

for n from 1 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: A225704(10^9, 4);

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 + 4, p - 4]] == {0}, AppendTo[t, n]; len = len + Length[IntegerDigits[n]] + 2]]; t (* T. D. Noe, May 17 2013 *)

CROSSREFS

Cf. A208728, A225702, A225703, A225705-A225720.

Sequence in context: A226494 A242920 A183072 * A228301 A193416 A315160

Adjacent sequences:  A225701 A225702 A225703 * A225705 A225706 A225707

KEYWORD

nonn

AUTHOR

Paolo P. Lava, May 13 2013

EXTENSIONS

Extended by T. D. Noe, May 17 2013

STATUS

approved

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Last modified August 5 19:30 EDT 2020. Contains 336213 sequences. (Running on oeis4.)