This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
import Data.List (isPrefixOf, find); import Data.Maybe (fromJust)
a018800 n = read $ fromJust $
find (show n `isPrefixOf`) $ map show a000040_list :: Int
-- Reinhard Zumkeller, Jul 01 2015
f:= proc(n) local x0, d,r,y;
if isprime(n) then return(n) fi;
for d from 1 do
x0:= n*10^d;
for r from 1 to 10^d-1 by 2 do
if isprime(x0+r) then
return(x0+r)
fi
od
od
end proc:
seq(f(n),n=1..100); # Robert Israel, Dec 23 2014
Table[Function[d, FromDigits@ SelectFirst[ IntegerDigits@ Prime@ Range[10^4], Length@ # >= Length@ d && Take[#, Length@ d] == d &]][ IntegerDigits@ n], {n, 59}] (* Michael De Vlieger, May 24 2016, Version 10 *)
a(n{,base=10}) = for (l=0, oo, forprime (p=n*base^l, (n+1)*base^l-1, return (p))) \\ Rémy Sigrist, Jun 11 2017
from sympy import isprime
def a(n):
if isprime(n): return n
pow10 = 10
while True:
t, maxt = n * pow10 + 1, (n+1) * pow10
while t < maxt:
if isprime(t): return t
t += 2
pow10 *= 10
print([a(n) for n in range(1, 60)]) # Michael S. Branicky, Nov 02 2021
Smallest prime formed from 20 is 1201, by placing 1 on both sides. Smallest prime formed from 33 is 233, by placing a 2 in front.
a068164 n = head (filter isPrime (digitExtensions n)) digitExtensions n = filter (includes n) [0..] includes n k = listIncludes (show n) (show k) listIncludes [] _ = True listIncludes (h:_) [] = False listIncludes l1@(h1:t1) (h2:t2) = if (h1 == h2) then (listIncludes t1 t2) else (listIncludes l1 t2) isPrime 1 = False isPrime n = not (hasDivisorAtLeast 2 n) hasDivisorAtLeast k n = (k*k <= n) && (((n `rem` k) == 0) || (hasDivisorAtLeast (k+1) n))
A068164 := proc(n) local p,pdigs,plen,dmas,dmasdigs,i,j; # test all primes ascending p := 2; while true do pdigs := convert(p,base,10) ; plen := nops(pdigs) ; # binary digit mask over p for dmas from 2^plen-1 to 0 by -1 do dmasdigs := convert(dmas,base,2) ; pdel := [] ; for i from 1 to nops(dmasdigs) do if op(i,dmasdigs) = 1 then pdel := [op(pdel),op(i,pdigs)] ; end if; end do: if n = add(op(j,pdel)*10^(j-1),j=1..nops(pdel)) then return p; end if; end do: p := nextprime(p) ; end do: end proc: seq(A068164(n),n=1..120) ; # R. J. Mathar, Nov 13 2014
from sympy import sieve
def dmo(n, t):
if t < n: return False
while n and t:
if n%10 == t%10:
n //= 10
t //= 10
return n == 0
def a(n):
return next(p for p in sieve if dmo(n, p))
print([a(n) for n in range(1, 77)]) # Michael S. Branicky, Jan 21 2023
0 appears first in 26th prime (101), so a(0) = 26; 9 appears first in 8th prime (19), so a(9) = 8; 24 appears first in 53rd prime (241), so a(24) = 53.
tg=101; T=0*Range[tg]; k=0; subs[n_] := Block[{d = IntegerDigits[n]}, Flatten@ Table[ FromDigits@ Take[d, {i, j}], {j, Length[d]}, {i, j}]]; While[tg > 0, s = subs[Prime[++k]]; Do[ If[e <= 100 && T[[e+1]] == 0, T[[e+1]] = k; tg--], {e, s}]]; T (* Giovanni Resta, Apr 29 2017 *)
a(n)={ my(q=prime(n), m=10^(logint(q,10)+1)); forprime(p=m, oo, my(x=p); while(x>=q, if(x%m==q, return(p)); x\=10)) } \\ Harry J. Smith, Sep 24 2009
a(3) = 36 since 3 occurs in 36, but not in 0, 1, 4, 9, 16, 25.
var sn,sq:string; b:boolean; end; begin for n := 0 to 49 do sn := itoa(n); c := length(sn); b := true; p := 0; while b do q := p^2; sq := itoa(q); d := length(sq); j := 0; while b and j<=d-c do if sn=sq[j..j+c-1] then b := false; write(q,","); else inc(j); end; end; if b then inc(p); end; end; end; end;
import Data.List (isPrefixOf, delete)
a258337 n = a258337_list !! (n-1)
a258337_list = f 1 $ map show a000040_list where
f x pss = g pss where
g (qs:qss) = if show x `isPrefixOf` qs
then (read qs :: Int) : f (x + 1) (delete qs pss)
else g qss
-- Reinhard Zumkeller, Jul 01 2015
N:= 100: # to get a(1) to a(N)
for n from 1 to N do
p:= n;
if n < 10 then
p1:= 0
else
p1:= A[floor(n/10)];
fi;
if isprime(p) and p > p1 then
A[n]:= p
else
for d from 1 while not assigned(A[n]) do
for i from 1 to 10^d-1 do
p:= 10^d*n+i;
if p > p1 and isprime(p) then
A[n]:= p;
break
fi;
od
od
fi
od:
seq(A[i],i=1..N); # Robert Israel, Jun 29 2015
sw(m,n)=d1=digits(n);d2=digits(m);for(i=1,min(#d1,#d2),if(d1[i]!=d2[i],return(0)));1 v=[];n=1;while(n<70,k=1;while(k<10^3,p=prime(k);if(sw(p,n)&&!vecsearch(vecsort(v),p),v=concat(v,p);k=0;n++);k++));v \\ Derek Orr, Jun 13 2015
f:= proc(n) local d,m,r;
for d from 1 do
for m from 1 to 10^d-1 by 2 do
r:= 10^d*n^2 + m;
if isprime(r) then return r fi
od od
end proc:
map(f, [$1..100]); # Robert Israel, May 16 2018
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