A068839 Smallest prime that ends with the right concatenation of first n odd numbers.

11, 31, 1531, 67531, 1397531, 311197531, 16131197531, 2515131197531, 71715131197531, 33191715131197531, 7621191715131197531, 232321191715131197531, 7252321191715131197531, 1327252321191715131197531, 322927252321191715131197531, 19312927252321191715131197531

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..200

Example

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

Mathematica

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}]
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 *)

Crossrefs

Cf. A068837, A068838.

Sequence in context: A111015 A143765 A023306 * A228530 A177360 A060857

Adjacent sequences: A068836 A068837 A068838 * A068840 A068841 A068842

Keyword

base,nonn

Author

Amarnath Murthy, Mar 10 2002

Extensions

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

More terms from Harvey P. Dale, May 25 2016

Status

approved