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A113008 Numbers n such that n, n+1, n+2, n+3 and n+4 are respectively 1,2,3,4,5-almost primes. 7
15121, 35521, 52321, 117841, 235441, 313561, 398821, 516421, 520021, 531121, 570601, 623641, 761113, 838561, 941041, 1117321, 1190821, 1317361, 1333621, 1336177, 1372081, 1413793, 1424041, 1431361, 1488901, 1513921, 1560121 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All listed terms are congruent to 1 modulo 12.

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

15121 is prime (or 1-almost prime), 15122=2*7561 is semiprime (or 2-almost prime), 15123=3*71*71 is 3-almost prime, 15124=2*2*29*199 is 4-almost prime, 15125=5*5*5*11*11 is 5-almost prime.

MATHEMATICA

f[n_] := Plus @@ Last /@ FactorInteger@n; t = {}; Do[p = Prime[n]; If[Array[ f[p + # ] &, 4] == {2, 3, 4, 5}, AppendTo[t, p]], {n, 126483}]; t (* Robert G. Wilson v *)

PROG

(Magma) [n: n in PrimesUpTo(2*10^6) | forall{k: k in [1..4] | &+[f[j, 2]: j in [1..#f]] eq k+1 where f is Factorization(n+k)}]; // Vincenzo Librandi, Sep 24 2012

(PARI) list(lim)=my(v=List(), L=(lim+2)\3, t); forprime(p=3, L\3, forprime(q=3, min(L\p, p), t=3*p*q-2; if(t%12==1 && isprime(t) && isprime((t+1)/2) && bigomega(t+3)==4 && bigomega(t+4)==5, listput(v, t)))); Set(v) \\ Charles R Greathouse IV, Feb 05 2017

CROSSREFS

Cf. A112998, A113000.

Sequence in context: A283527 A190294 A124047 * A004935 A004955 A004975

Adjacent sequences: A113005 A113006 A113007 * A113009 A113010 A113011

KEYWORD

nonn,easy

AUTHOR

Zak Seidov, Jan 03 2006

EXTENSIONS

More terms from Robert G. Wilson v, Jan 05 2006

STATUS

approved

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Last modified December 1 23:44 EST 2022. Contains 358485 sequences. (Running on oeis4.)