A106553 - OEIS

A106553

Semiprime + (largest integer obtained by concatenating its two divisors).

26, 38, 42, 62, 86, 68, 94, 233, 80, 239, 344, 251, 110, 257, 352, 278, 126, 368, 566, 376, 350, 374, 578, 392, 446, 788, 494, 602, 518, 416, 804, 424, 566, 614, 638, 484, 638, 710, 836, 1232, 734, 536, 562, 852, 806, 614, 854, 1454, 674, 878, 686, 950, 692

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..53.

EXAMPLE

First semiprime is 4; 4 is 2*2; 26=4+22.

Second semiprime is 6; 6 is 2*3 (23) or 3*2 (32); 38=6+32.

...

Eighth semiprime is 22; 22 is 2*11 (211) or 11*2 (112); 233=22+211.

MATHEMATICA

licd[n_]:=Module[{fi=Flatten[Table[#[[1]], #[[2]]]&/@FactorInteger[n], 1]}, Max[fi[[1]]*10^IntegerLength[ fi[[2]]]+fi[[2]], fi[[2]]*10^IntegerLength[ fi[[1]]]+fi[[1]]]+n]; licd/@(Select[Range[200], PrimeOmega[#]==2&]) (* Harvey P. Dale, Jul 22 2019 *)

CROSSREFS

Cf. A001358, A106552

Sequence in context: A171745 A045092 A106551 * A371696 A178662 A039324

Adjacent sequences: A106550 A106551 A106552 * A106554 A106555 A106556

KEYWORD

base,easy,nonn

AUTHOR

Eric Angelini, May 09 2005

EXTENSIONS

Corrected and extended by Harvey P. Dale, Jul 22 2019

STATUS

approved