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A117273 Numbers n for which the product of the digits equals the number of prime numbers smaller than n. 0
16, 53, 63, 364, 437, 545, 573, 829, 963, 5449, 6475, 23797, 67458, 2475998 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This sequence is finite with its largest term < 10^70. - Stefan Steinerberger, Apr 24 2006

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

364 is in the sequence because (1)the product of its digits is 3*6*4=72 and (2) there are 72 prime numbers smaller than 364.

MATHEMATICA

Select[Range[50000], DigitCount[ # ][[10]] == 0 && Product[i^DigitCount[ # ][[i]], {i, 1, 9}] == PrimePi[ # - 1] &] (* Stefan Steinerberger, Apr 24 2006 *)

g[n_] := Product[IntegerDigits[n][[m]], {m, 1, Length[IntegerDigits[n]]}]; Do[If[g[n] == PrimePi[n], Print[n]], {n, 1, 10000000}] (* Mohammed Bouayoun (Mohammed.bouayoun(AT)sanef.com), Apr 24 2006 *)

CROSSREFS

Cf. A000720, A097220.

Sequence in context: A232509 A087973 A332591 * A137515 A164324 A334643

Adjacent sequences:  A117270 A117271 A117272 * A117274 A117275 A117276

KEYWORD

base,more,nonn,fini

AUTHOR

Luc Stevens (lms022(AT)yahoo.com), Apr 23 2006

EXTENSIONS

More terms from Zak Seidov, Stefan Steinerberger and Mohammed Bouayoun (Mohammed.bouayoun(AT)sanef.com), Apr 24 2006

STATUS

approved

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Last modified September 22 16:50 EDT 2020. Contains 337291 sequences. (Running on oeis4.)