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 A117273 Numbers m such that the product of the digits of m is equal to the number of primes less than m. 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 a(15) > 1.288 * 10^10 if it exists. - Kevin P. Thompson, Oct 19 2021 LINKS Table of n, a(n) for n=1..14. EXAMPLE 364 is in the sequence because the product of its digits is 3*6*4 = 72 and 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 *) PROG (PARI) isok(m) = vecprod(digits(m)) == primepi(m); \\ Michel Marcus, Oct 23 2021 CROSSREFS Cf. A000720, A007954, A097220. Sequence in context: A087973 A351584 A332591 * A137515 A164324 A334643 Adjacent sequences: A117270 A117271 A117272 * A117274 A117275 A117276 KEYWORD nonn,base,fini,more 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 21 02:47 EDT 2023. Contains 365486 sequences. (Running on oeis4.)