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A032758
Undulating primes (digits alternate).
38
2, 3, 5, 7, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 131, 151, 181, 191, 313, 353, 373, 383, 727, 757, 787, 797, 919, 929, 18181, 32323, 35353, 72727, 74747, 78787, 94949, 95959, 1212121, 1616161, 323232323, 383838383
OFFSET
1,1
COMMENTS
Sometimes called "smoothly undulating primes", to distinguish them from A059168.
REFERENCES
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
Michael S. Branicky, Table of n, a(n) for n = 1..131 (terms 1..100 from Sean A. Irvine)
C. A. Pickover, "Wonders of Numbers, Adventures in Mathematics, Mind and Meaning," Zentralblatt review
Charles W. Trigg, Nine-digit patterned palindromic primes, Crux Mathematicorum, Vol. 7, No. 6, June - July 1981, pp. 168-170.
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 && a[p][[1]] != b[p][[1]], AppendTo[t, p]]], {n, 3*10^7}]; t (* Jayanta Basu, May 04 2013 *)
PROG
(Python)
from itertools import count, islice
from sympy import isprime, primerange
def agen(): # generator of terms
yield from (p for p in primerange(2, 100) if p != 11)
yield from (t for t in (int((A+B)*d2+A) for d2 in count(1) for A in "1379" for B in "0123456789" if A != B) if isprime(t))
print(list(islice(agen(), 51))) # Michael S. Branicky, Jun 09 2022
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Patrick De Geest, May 15 1998
EXTENSIONS
Sequence corrected by Juri-Stepan Gerasimov, Jan 28 2010
Offset corrected by Arkadiusz Wesolowski, Sep 13 2011
STATUS
approved