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A104424 Numbers n such that n, prime(n), prime(n)+n, prime(n)-n and prime(n)*n all lack the digit 4. 2
1, 2, 3, 5, 6, 8, 10, 22, 23, 26, 27, 28, 29, 31, 39, 57, 58, 62, 66, 112, 120, 122, 125, 126, 129, 130, 131, 135, 137, 139, 152, 153, 178, 182, 183, 192, 196, 210, 211, 212, 213, 216, 220, 221, 222, 250, 280, 285, 286, 287, 291, 293, 295, 299, 300, 303, 305, 306 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

From the first 3000 primes, only 289 are such that n, p[n], p[n]+n, p[n]-n and p[n]*n all are 4-less.

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MAPLE

fourless:= n -> not has(4, convert(n, base, 10)):

p:= 1: R:= NULL: count:= 0:

for n from 1 while count < 100 do

  p:= nextprime(p);

  if andmap(fourless, [n, p, p+n, p-n, p*n]) then

    count:= count+1; R:= R, n;

  fi

od:

R; # Robert Israel, Apr 23 2020

MATHEMATICA

id[x_]:=IntegerDigits[x]; pr[i_]:=Prime[i]; ra=Range[3000]; A104424=Select[ra, Position[Union[id[ # ], id[pr[ # ]], id[pr[ # ]+# ], id[pr[ # ]-# ], id[pr[ # ]*# ]], 4]=={}&]

CROSSREFS

Cf. A104419-A104428.

Sequence in context: A252482 A124145 A188064 * A028806 A028731 A028740

Adjacent sequences:  A104421 A104422 A104423 * A104425 A104426 A104427

KEYWORD

nonn,base

AUTHOR

Zak Seidov, Mar 07 2005

EXTENSIONS

Name edited by Robert Israel, Apr 23 2020

STATUS

approved

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Last modified September 23 19:03 EDT 2021. Contains 347617 sequences. (Running on oeis4.)