OFFSET
1,1
COMMENTS
In the first 250000 terms the largest value is a(203564) = 30. See the examples.
See A369353 for the numbers that terminate the series with lengths >= 1.
LINKS
Scott R. Shannon, Table of n, a(n) for n = 1..10000
EXAMPLE
a(1) = 12. See A369348 for further information.
a(2) = 0 as there is no number k such that k - 2 = sopfr(k) + sopfr(2).
a(5) = 2 as the series when starting at 5 is 5, 18, 36, and there is no number k such that k - 36 = sopfr(k) + sopfr(36).
a(203564) = 30 as the series when starting at 203564 is 203564, 279917, 305772, 306383, 307737, 309072, 618538, 1237084, 1547240, 1549668, 1555427, 1689623, 1850460, 1897986, 1978513, 2170033, 2300849, 2307769, 2313234, 4629862, 6952637, 6966959, 7000937, 8032504, 9080469, 9125207, 9266466, 14110329, 28220667, 37702139, 37817849, and there is no number k such that k - 37817849 = sopfr(k) + sopfr(37817849).
CROSSREFS
KEYWORD
nonn
AUTHOR
Scott R. Shannon, Jan 21 2024
STATUS
approved