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A067087 Concatenation of n-th prime and its reverse. 7

%I #10 Nov 11 2017 13:01:16

%S 22,33,55,77,1111,1331,1771,1991,2332,2992,3113,3773,4114,4334,4774,

%T 5335,5995,6116,6776,7117,7337,7997,8338,8998,9779,101101,103301,

%U 107701,109901,113311,127721,131131,137731,139931,149941,151151,157751

%N Concatenation of n-th prime and its reverse.

%H Harry J. Smith, <a href="/A067087/b067087.txt">Table of n, a(n) for n = 1..1000</a>

%F Every term of the sequence is divisible by 11.

%t Table[ ToExpression[ StringJoin[ ToString[Prime[n]], StringReverse[ ToString[ Prime[n]]]]], {n, 1, 40} ]

%t #*10^IntegerLength[#]+IntegerReverse[#]&/@Prime[Range[50]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Nov 11 2017 *)

%o (PARI) digitsIn(x)= { local(d); if (x==0, return(1)); d=1 + log(x)\log(10); if (10^d == x, d++, if (10^(d-1) > x, d--)); return(d) } Concat(a, b)= { return(a*10^digitsIn(b) + b) } Rev(x)= { local(d, r=0); while (x>0, d=x%10; x\=10; r=r*10 + d); return(r) } { for (n=1, 1000, p=prime(n); write("b067087.txt", n, " ", Concat(p, Rev(p))) ) } \\ _Harry J. Smith_, May 13 2010

%K easy,nonn,base

%O 1,1

%A _Amarnath Murthy_, Jan 07 2002

%E More terms from _Robert G. Wilson v_, Jan 09 2002

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Last modified July 25 04:49 EDT 2024. Contains 374586 sequences. (Running on oeis4.)