A245024 -id:A245024 - cp's OEIS frontend

A242060 Lpf_3(A242058(n)-3), where lpf_3(n) = lpf(n/3^t) (cf. A020639) such that 3^t (t>=0) is the maximal power of 3 which divides n.

1, 5, 1, 11, 5, 17, 7, 1, 29, 5, 13, 41, 5, 7, 17, 5, 19, 59, 5, 23, 71, 5, 7, 1, 5, 29, 7, 5, 11, 101, 5, 107, 37, 5, 7, 11, 5, 43, 5, 137, 5, 7, 149, 5, 7, 5, 13, 19, 5, 59, 179, 5, 7, 191, 5, 197, 5, 11, 5, 7, 13, 5, 227, 7, 5, 79, 239, 1, 5, 13, 83, 5, 7

Offset: 1

Vladimir Shevelev, Aug 13 2014

nonn

An analog of A242034. Records are lesser numbers of twin primes.

Cf. A245024, A243937, A242057, A242058, A242059, A242033, A242034.

lpf[n_]:=lpf[n]=First[First[FactorInteger[n]]];
lpf3[n_]:=lpf3[n]=If[#==1,1,lpf[#]]&[n/3^IntegerExponent[n,3]]
Map[lpf3[#-3]&,Select[Range[4,300,2],lpf3[#-1]>lpf3[#-3]&]](* Peter J. C. Moses, Aug 13 2014 *)

More terms from Peter J. C. Moses, Aug 13 2014

A245274 Composite terms in sequence {A243937(n)-1}.

Original entry on oeis.org

35, 65, 77, 95, 119, 121, 125, 143, 155, 161, 185, 187, 203, 209, 215, 217, 221, 245, 247, 275, 287, 289, 299, 305, 323, 329, 335, 341, 365, 371, 377, 395, 407, 413, 425, 427, 437, 455, 473, 485, 497, 515, 517, 527, 529, 533, 539, 545, 551, 575, 581, 583, 605

Offset: 1

Vladimir Shevelev, Jul 16 2014

nonn

See comment in A243937.
If prime p is not in A062326, then p^2 is in the sequence.
If p>3 and p,p+2 are twin primes, then p*(p+2) is in the sequence. Indeed, it can be shown that in this case (p+1)^2 is in A243937. lpf((p+1)^2-1)=p while lpf((p+1)^2-3)=3, since for lesser p>3 of twin prime p+1==0(mod 6).

Cf. A245272, A243937, A245024.

More terms from Peter J. C. Moses, Jul 16 2014

cp's OEIS Frontend

A242060 Lpf_3(A242058(n)-3), where lpf_3(n) = lpf(n/3^t) (cf. A020639) such that 3^t (t>=0) is the maximal power of 3 which divides n.

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