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A036343
Prime concatenated analog clock numbers read counterclockwise.
4
2, 3, 5, 7, 11, 43, 109, 10987, 76543, 6543211211, 4321121110987, 3211211109876543211211, 43211211109876543211211109876543, 9876543211211109876543211211109876543211211109876543211211
OFFSET
1,1
COMMENTS
The hours 10, 11 and 12 are taken 'complete and unreversed'.
a(19) has 1139 digits. - Michael S. Branicky, May 20 2024
LINKS
Carlos Rivera, Puzzle 19. Primes on a clock, The Prime Puzzles & Problems Connection.
Eric Weisstein's World of Mathematics, Clock Prime.
PROG
(Python)
import heapq
from sympy import isprime
from itertools import islice
def A036343_gen(): # generator of terms
h = [(i, i) for i in range(1, 13)]
while True:
v, last = heapq.heappop(h)
if isprime(v):
yield v
nxt = 12 if last == 1 else last-1
shift = 10 if nxt < 10 else 100
heapq.heappush(h, (v*shift+nxt, nxt))
print(list(islice(A036343_gen(), 16))) # Michael S. Branicky, May 20 2024
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Dec 15 1998
EXTENSIONS
Offset corrected by Sean A. Irvine, Oct 26 2020
STATUS
approved