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 A059170 Strictly undulating primes (digits alternate and differ by 1). 1
 2, 3, 5, 7, 23, 43, 67, 89, 101, 787, 32323, 78787, 1212121, 323232323, 989898989, 12121212121, 32323232323, 787878787878787878787, 787878787878787878787878787, 1212121212121212121212121212121212121212121 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The next two terms have 95 and 139 digits respectively.  [Jayanta Basu, May 09 2013] REFERENCES Of form ababa... with |a-b| = 1. C. A. Pickover, "Keys to Infinity", Wiley 1995, p. 159,160. C. A. Pickover, "Wonders of Numbers", Oxford New York 2001, Chapter 52, pp. 123-124, 316-317. LINKS P. De Geest, More undulating primes C. A. Pickover, "Wonders of Numbers, Adventures in Mathematics, Mind and Meaning," Zentralblatt review MATHEMATICA a[n_]:=DeleteDuplicates[Take[IntegerDigits[n], {1, -1, 2}]]; b[n_]:=DeleteDuplicates[Take[IntegerDigits[n], {2, -1, 2}]]; t={}; Do[p=Prime[n]; If[p<10, AppendTo[t, p], If[Length[a[p]] == Length[b[p]] == 1 && Abs[a[p][[1]]-b[p][[1]]] == 1, AppendTo[t, p]]], {n, 10^5}]; t (* Jayanta Basu, May 08 2013 *) t1=Join[{2, 3, 5, 7}, Select[Range[10, 100], PrimeQ[#]&&Abs[Differences[IntegerDigits[#]]]=={1}&]]; Do[a=n*10+(n-1); b=(n-1)*10+n; t1=Join[t1, Select[Table[(a*10^(2*n+1)-b)/99, {n, 25}], PrimeQ]]; If[n<=7, c=n*10+(n+1); d=(n+1)*10+n; t1=Join[t1, Select[Table[(c*10^(2*n+1)-d)/99, {n, 25}], PrimeQ]]], {n, 1, 9, 2}]; Sort[t1] (* Jayanta Basu, May 09 2013 *) CROSSREFS Cf. A032758, A059168, A048398, A033619, A046075, A059758. Sequence in context: A106711 A235110 A048398 * A068710 A120805 A177119 Adjacent sequences:  A059167 A059168 A059169 * A059171 A059172 A059173 KEYWORD nonn,base AUTHOR N. J. A. Sloane, Feb 14 2001 EXTENSIONS Extended by Patrick De Geest, Feb 25 2001. Offset corrected by Arkadiusz Wesolowski, Sep 13 2011 STATUS approved

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