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 A018847 Strobogrammatic primes: the same upside down (calculator-style numerals). 7
 2, 5, 11, 101, 151, 181, 619, 659, 6229, 10501, 12821, 15551, 16091, 18181, 19861, 60209, 60509, 61519, 61819, 62129, 116911, 119611, 160091, 169691, 191161, 196961, 605509, 620029, 625529, 626929, 650059, 655559, 656959, 682289, 686989, 688889 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This is the subsequence of primes in A018846. - M. F. Hasler, May 05 2012 LINKS M. F. Hasler, Table of n, a(n) for n = 1..648 MATHEMATICA lst = {}; fQ[n_] := Block[{allset = {0, 1, 2, 5, 6, 8, 9}, id = IntegerDigits@n}, Union@ Join[id, allset] == allset && Reverse[id /. {6 -> 9, 9 -> 6}] == id]; Do[ If[ PrimeQ@n && fQ@n, AppendTo[lst, n]], {n, 700000}]; lst (* Robert G. Wilson v, Feb 27 2007 *) PROG (PARI) {write("/tmp/b018847.txt", "1 2\n2 5"); c=2; s2=[0, 1, 2, 5, 6, 8, 9]; s=[0, 1, 2, 5, 8]; s1=[0, 1, 2, 5, 9, 8, 6]; for(n=2, 9, p1=vector( (n+1)\2, i, 10^(i-1)); p2=vector( (n+1)\2, i, 10^(n-i)); forvec( v=vector((n+1)\2, i, if( i>1, [ 1, if( i>n\2, #s, #s1)], [2, 5])), v[1]==3 & v[1]=5; ispseudoprime( t=sum(i=1, n\2, p1[i]*s1[v[i]]+p2[i]*s2[v[i]] ) +if(n%2, p1[#p1]*s[v[#v]] )) & /* print1(t", ") */ write("/tmp/b018847.txt", c++" "t)))} \\ - M. F. Hasler, Apr 26 2012 (PARI) is_A018847(n, t=Vec("012..59.86"))={ isprime(n) & apply(x->t[eval(x)+1], n=Vec(Str(n)))==vecextract(n, "-1..1") } \\ - M. F. Hasler, May 05 2012 CROSSREFS Cf. A007597 (more restrictive version not allowing digits 2 or 5). Sequence in context: A267527 A286453 A309375 * A178318 A134996 A134998 Adjacent sequences: A018844 A018845 A018846 * A018848 A018849 A018850 KEYWORD nonn,base AUTHOR David W. Wilson STATUS approved

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Last modified September 28 01:19 EDT 2023. Contains 365714 sequences. (Running on oeis4.)