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A062238
Composite numbers which contain their largest proper divisor as a substring.
14
15, 25, 125, 1537, 3977, 11371, 38117, 110317, 117197, 123679, 143323, 146137, 179297, 197513, 316619, 390913, 397139, 399797, 485357, 779917, 797191, 990919, 1110691, 1178951, 1483117, 1723717, 1813733, 2165299, 2273099, 2369777, 2947969, 3035171, 3099013, 3183113
OFFSET
1,1
LINKS
EXAMPLE
3{97}7 = 97*41.
MATHEMATICA
Do[ If[ !PrimeQ[ n ] && StringPosition[ ToString[ n ], ToString[ Divisors[ n ] [ [ -2 ] ] ] ] != {}, Print[ n ] ], {n, 2, 10^7} ]
Select[Range[319*10^4], CompositeQ[#]&&SequenceCount[IntegerDigits[ #], IntegerDigits[ Divisors[#][[-2]]]]>0&] (* Harvey P. Dale, Dec 26 2022 *)
PROG
(PARI) gpd(n) = if(n==1, 1, n/factor(n)[1, 1]); \\ A032742
issub(vv, v) = {for (i=1, #v - #vv + 1, if (vector(#vv, k, v[k+i-1]) == vv, return(1)); ); }
isok(n) = if ((n>1) && !isprime(n), issub(digits(gpd(n)), digits(n))); \\ Michel Marcus, Dec 31 2020
CROSSREFS
Cf. A002808 (composite numbers), A032742.
Sequence in context: A032587 A336689 A347375 * A146249 A248834 A249109
KEYWORD
base,nonn
AUTHOR
Erich Friedman, Jun 30 2001
EXTENSIONS
More terms from Robert G. Wilson v, Aug 08 2001
More terms from Michel Marcus, Dec 31 2020
Clarified definition at the suggestion of Harvey P. Dale. - N. J. A. Sloane, Dec 26 2022
STATUS
approved