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A256227 Naught-y numbers (A011540) that after removing all zeros become zeroless primes (A038618). 1
20, 30, 50, 70, 101, 103, 107, 109, 110, 130, 170, 190, 200, 203, 209, 230, 290, 300, 301, 307, 310, 370, 401, 403, 407, 410, 430, 470, 500, 503, 509, 530, 590, 601, 607, 610, 670, 700, 701, 703, 709, 710, 730, 790, 803, 809, 830, 890, 907, 970, 1001, 1003, 1007, 1009, 1010, 1013, 1027, 1030 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..58.

MAPLE

N:= 4: # to produce all terms with <= N digits

ZLO:= proc(d) # produce set of d-digit odd zeroless numbers

       option remember;

       if d = 1 then {1, 3, 5, 7, 9}

       else

         map(t -> seq(t+x*10^(d-1), x=1..9), ZLO(d-1))

       fi

end proc:

addzeros:= proc(x, d) # d-digit numbers formed by inserting 0's into x

        local L, n, R;

      L:= convert(x, base, 10);

      n:= nops(L);

      R:= map(t -> [op(t), d], combinat[choose](d-1, n-1));

      seq(add(L[i]*10^(r[i]-1), i=1..n), r = R);

    end proc:

Z[1]:= {2, 3, 5, 7}:

for i from 2 to N-1 do Z[i]:= select(isprime, ZLO(i)) od:

`union`(seq(seq(map(addzeros, Z[i], d), i=1..d-1), d=2..N));

# if using Maple 11 or earlier, uncomment the next line

# sort(convert(%, list)); # Robert Israel, Mar 19 2015

MATHEMATICA

ss={}; Do[id=IntegerDigits[p]; If[Min[id]<1&&PrimeQ[FromDigits[Delete[id, Position[id, 0]]]], ss={ss, p}], {p, 20, 2000}]; Flatten[ss]

PROG

(PARI) is(n)=my(d=digits(n), e=select(x->x, d)); #e<#d && isprime(fromdigits(e)) \\ Charles R Greathouse IV, Mar 19 2015

CROSSREFS

A256186 is the intersection of this sequence with A000040.

Cf. A011540, A038618, A056709.

Sequence in context: A104048 A078499 A066027 * A142342 A008444 A268984

Adjacent sequences:  A256224 A256225 A256226 * A256228 A256229 A256230

KEYWORD

nonn,base

AUTHOR

Charles R Greathouse IV and Zak Seidov, Mar 19 2015

STATUS

approved

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Last modified February 19 03:54 EST 2020. Contains 332032 sequences. (Running on oeis4.)