A068839 - OEIS

%I #9 May 25 2016 10:32:08

%S 11,31,1531,67531,1397531,311197531,16131197531,2515131197531,

%T 71715131197531,33191715131197531,7621191715131197531,

%U 232321191715131197531,7252321191715131197531,1327252321191715131197531,322927252321191715131197531,19312927252321191715131197531

%N Smallest prime that ends with the right concatenation of first n odd numbers.

%H Harvey P. Dale, <a href="/A068839/b068839.txt">Table of n, a(n) for n = 1..200</a>

%e a(5) = 1397531 which contains as trailing digits the right concatenation of first 5 odd numbers 97531.

%t a068839[n_] := Module[{}, a1=Flatten[Table[IntegerDigits[i], {i, n, 1, -2}]]; FromDigits[pref=1; a2=a1; While[ !PrimeQ[FromDigits[a2]], a2=Join[IntegerDigits[pref], a1]; pref+=1]; a2]]; Table[a068839[i], {i, 1, 33, 2}]

%t sp[n_]:=Module[{k=0,r=FromDigits[Flatten[IntegerDigits/@Reverse[Range[1,n,2]]]]}, While[ !PrimeQ[ k*10^IntegerLength[r]+r],k++];k*10^IntegerLength[r]+r]; Table[ sp[i], {i,1,33,2}] (* _Harvey P. Dale_, May 25 2016 *)

%Y Cf. A068837, A068838.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Mar 10 2002

%E More terms from Vit Planocka (planocka(AT)mistral.cz), Oct 18 2002

%E More terms from _Harvey P. Dale_, May 25 2016