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 A120383 A number n is included if it satisfies: m divides n for all m's where the m-th prime divides n. 26
 1, 2, 4, 6, 8, 12, 16, 18, 24, 28, 30, 32, 36, 48, 54, 56, 60, 64, 72, 78, 84, 90, 96, 108, 112, 120, 128, 144, 150, 152, 156, 162, 168, 180, 192, 196, 216, 224, 234, 240, 252, 256, 270, 288, 300, 304, 312, 324, 330, 336, 360, 384, 390, 392, 414, 420, 432, 444, 448 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS From Rémy Sigrist, Apr 08 2017: (Start) If n is in the sequence, then 2*n is also in the sequence. a(2) = 2 is the only prime number in the sequence. a(1) = 1 is the only odd number in the sequence. (End) Numbers divisible by all of their prime indices. A prime index of n is a number m such that prime(m) divides n. For example, the prime indices of 78 = prime(1) * prime(2) * prime(6) are {1,2,6}, all of which divide 78, so 78 is in the sequence. - Gus Wiseman, Mar 23 2019 LINKS Rémy Sigrist, Table of n, a(n) for n = 1..10000 EXAMPLE 28 = 2^2 * 7. 2 is the first prime, 7 is the 4th prime. Since 1 and 4 both divide 28, then 28 is included in the sequence. 78 = 2 * 3 * 13. 2 is the first prime, 3 is the 2nd prime and 13 is the 6th prime. Since 1 and 2 and 6 each divide 78, then 78 is in the sequence. (Note that 1 * 2 * 6 does not divide 78.) From Gus Wiseman, Mar 23 2019: (Start) The sequence of terms together with their prime indices begins:    1: {}    2: {1}    4: {1,1}    6: {1,2}    8: {1,1,1}   12: {1,1,2}   16: {1,1,1,1}   18: {1,2,2}   24: {1,1,1,2}   28: {1,1,4}   30: {1,2,3}   32: {1,1,1,1,1}   36: {1,1,2,2}   48: {1,1,1,1,2}   54: {1,2,2,2}   56: {1,1,1,4}   60: {1,1,2,3}   64: {1,1,1,1,1,1} (End) MAPLE A000040inv := proc(n) local i; i:=1 ; while true do if ithprime(i) = n then RETURN(i) ; fi ; i := i+1 ; end ; end: isA120383 := proc(n) local pl, p, i, j ; pl := ifactors(n) ; pl := pl ; for i from 1 to nops(pl) do p := pl[i] ; j := A000040inv(p) ; if n mod j <> 0 then RETURN(false) ; fi ; od ; RETURN(true) ; end: for n from 2 to 800 do if isA120383(n) then printf("%d, ", n); fi ; od ; # R. J. Mathar, Sep 02 2006 MATHEMATICA {1}~Join~Select[Range[2, 450], Function[n, AllTrue[PrimePi /@ FactorInteger[n][[All, 1]], Mod[n, #] == 0 &]]] (* Michael De Vlieger, Mar 24 2019 *) PROG (PARI) ok(n) = my (f=factor(n)); for (i=1, #f~, if (n % primepi(f[i, 1]), return (0))); return (1) \\ Rémy Sigrist, Apr 08 2017 CROSSREFS Cf. A000720, A003963, A056239, A112798, A323440, A324846, A324847, A324848, A324850, A324852, A324856. Sequence in context: A060765 A140110 A128397 * A324842 A055932 A140067 Adjacent sequences:  A120380 A120381 A120382 * A120384 A120385 A120386 KEYWORD nonn AUTHOR Leroy Quet, Jun 29 2006 EXTENSIONS More terms from R. J. Mathar, Sep 02 2006 Initial 1 prepended by Rémy Sigrist, Apr 08 2017 STATUS approved

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Last modified February 20 04:47 EST 2020. Contains 332063 sequences. (Running on oeis4.)