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A147627 Numbers n = concat(a,b) such that bigomega(n) = bigomega(a) * bigomega(b), where bigomega = A001222. 3
23, 26, 28, 34, 37, 39, 53, 62, 65, 73, 74, 78, 93, 95, 104, 113, 119, 125, 134, 137, 138, 142, 143, 145, 155, 156, 173, 182, 193, 194, 197, 207, 211, 212, 213, 214, 215, 217, 221, 223, 226, 229, 230, 233, 235, 238, 241, 242, 244, 245, 249, 253, 260, 262, 265 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Concat(a,b) means decimal concatenation of a and b, i.e., a*10^[log[10](b)+1] + b, since we do not allow leading zeros in b.

LINKS

Table of n, a(n) for n=1..55.

EXAMPLE

a(4)=34 is in the sequence since bigomega(34) = 2 = 1*2 = bigomega(3)*bigomega(4).

206 is not in this sequence although bigomega(206) = 2 = 1*2 = bigomega(2)*bigomega(06), we do not allow leading zeros in the second part b.

PROG

(PARI) is_A147627(n)={ local(p=1, o=bigomega(n)); while( n>p*=10, n%p*10<p & next; o == bigomega( n\p )* bigomega( n%p ) & return(1))}

for( n=1, 999, is_A147627(n) & print1(n", "))

CROSSREFS

Cf. A001222, A147616 (analog for sigma), A147619 (analog for eulerphi), A147624 (analog for omega).

Sequence in context: A112073 A050864 A111452 * A025059 A316724 A160774

Adjacent sequences:  A147624 A147625 A147626 * A147628 A147629 A147630

KEYWORD

base,easy,nonn

AUTHOR

M. F. Hasler, Nov 08 2008

STATUS

approved

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Last modified March 19 17:21 EDT 2019. Contains 321330 sequences. (Running on oeis4.)