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 A106554 Concatenation of the two divisors of a semiprime, smallest divisor first. 5
 22, 23, 33, 25, 27, 35, 37, 211, 55, 213, 311, 217, 57, 219, 313, 223, 77, 317, 511, 319, 229, 231, 513, 323, 237, 711, 241, 517, 243, 329, 713, 331, 247, 519, 253, 337, 523, 259, 717, 1111, 261, 341, 343, 719, 267, 347, 271, 1113 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Concatenation of the divisors starting with the largest one leads to another sequence. LINKS Michael De Vlieger, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A037276(A001358(n)). - R. J. Mathar, Oct 29 2012 EXAMPLE First semiprime is 4; 4 is 2*2 -> 22. Second semiprime is 6; 6 is 2*3 -> 23. Third semiprime is 9; 9 is 3*3 -> 33. Fourth semiprime is 10; 10 is 2*5 -> 25. MAPLE read("transforms") : A106554 := proc(n) A037276(A001358(n)) ; end proc: # R. J. Mathar, Oct 29 2012 MATHEMATICA FromDigits@ Flatten[IntegerDigits@ Table[#1, {#2}] & @@@ FactorInteger@ #] & /@ Select[Range@ 144, PrimeOmega@ # == 2 &] (* Michael De Vlieger, Oct 01 2015 *) PROG (PARI) do(x)=my(v=List()); forprime(p=2, sqrt(x), forprime(q=p, x\p, listput(v, [p*q, eval(Str(p, q))]))); Vec(apply(u->u[2], vecsort(v, 1))) \\ Charles R Greathouse IV, Sep 30 2015 CROSSREFS Cf. A106550, A084126, A084127, A001358. Sequence in context: A114963 A146755 A106556 * A118297 A022392 A041976 Adjacent sequences: A106551 A106552 A106553 * A106555 A106556 A106557 KEYWORD base,easy,nonn AUTHOR Eric Angelini, May 09 2005 EXTENSIONS More terms from Reinhard Zumkeller, May 19 2005 Data corrected by Giovanni Teofilatto and Altug Alkan, Oct 01 2015 STATUS approved

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Last modified November 30 18:31 EST 2023. Contains 367461 sequences. (Running on oeis4.)