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 A049529 Numbers n such that sum of factorials of digits of n equals pi(n) (A000720). 3
 6500, 6501, 6510, 6511, 6521, 12066, 50372, 175677, 553783, 5224903, 5224923, 5246963, 5302479, 5854093, 5854409, 5854419, 5854429, 5854493, 5855904, 5864049, 5865393, 10990544, 11071599 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS By the time that n = 10^8 the number of primes <= 10^8 (5761455) exceeds 8*9! (2903040). - Robert G. Wilson v, Jan 16 2002 LINKS C. Caldwell and G. L. Honaker, Jr., Is pi(6521)=6!+5!+2!+1! unique?, Math. Spectrum, 22:2 (2000/2001) 34-36. Shyam Sunder Gupta, Fascinating Factorials G. L. Honaker, Jr. and Chris Caldwell, Prime Curios! 6521 Eric Weisstein's World of Mathematics, Factorial EXAMPLE a(10)=5224903 because there are exactly 5!+2!+2!+4!+9!+0!+3! (or 363035) prime numbers less than or equal to 5224903. MATHEMATICA Do[ If[ Apply[ Plus, IntegerDigits[n] ! ] == PrimePi[n], Print[n]], {n, 1, 11100000} ] PROG (PARI) isok(n) = my(d=digits(n)); sum(k=1, #d, d[k]!) == primepi(n); \\ Michel Marcus, Nov 07 2018 CROSSREFS Cf. A000720, A049530. Sequence in context: A031842 A028544 A237245 * A284102 A338951 A251447 Adjacent sequences:  A049526 A049527 A049528 * A049530 A049531 A049532 KEYWORD fini,full,nonn,base AUTHOR G. L. Honaker, Jr., Sep 15 1999 STATUS approved

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Last modified August 14 17:10 EDT 2022. Contains 356122 sequences. (Running on oeis4.)