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A225298 Smallest pandigital number with exactly n prime factors (with multiplicity). 0
10123457689, 10123456789, 1023456879, 1023456987, 1023456897, 1023456789, 1023456798, 1023457896, 1023486975, 1023479856, 1023458976, 1023475968, 1024973568, 1023579648, 1024897536, 1023657984, 1032984576, 1034698752, 1093865472, 1074659328, 1072963584 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Smallest pandigital n-almost prime.

LINKS

Table of n, a(n) for n=1..21.

FORMULA

a(n) = MIN{k such that k is in A050278 and bigomega(k) = n}.

a(n) = MIN{k such that k is in A050278 and A001222(k) = n}.

EXAMPLE

a(1) = 10123457689 is the least prime pandigital number (A221646), that is, the smallest prime containing all the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.

a(2) = 10123456789 = 919 * 11015731, the smallest pandigital semiprime.

a(3) = 1023456879, the smallest pandigital number (A171102) that is 3-almost prime (product of three primes with repetition).

a(4) = 1023456987 = 3^2 * 7 * 16245349, which is the smallest pandigital 4-almost prime.

a(5) = 1023456897 = 3^3 * 2417 * 15683.

a(6) = 1023456789 = 3^4 * 2221 * 5689.

a(7) = 1023456798 = 2 * 3^2 * 7 * 13 * 487 * 1283.

a(8) = 1023457896 = 2^3 * 3^3 * 59 * 80309.

MATHEMATICA

a[n_] := Block[{k = If[n < 3, 10123456789, 1023456789]}, While[ Union@ IntegerDigits@ k != Range[0, 9] || Total[Last /@ FactorInteger[k]] != n, k++]; k]; Array[a, 10] (* Giovanni Resta, May 06 2013 *)

CROSSREFS

Cf. A171102, A221646, A175845.

Sequence in context: A296158 A172688 A112388 * A050288 A173051 A159569

Adjacent sequences:  A225295 A225296 A225297 * A225299 A225300 A225301

KEYWORD

nonn,base,easy

AUTHOR

Jonathan Vos Post, May 04 2013

EXTENSIONS

a(2) corrected and a(9)-a(21) from Giovanni Resta, May 06 2013

STATUS

approved

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Last modified April 7 10:56 EDT 2020. Contains 333301 sequences. (Running on oeis4.)