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A369348
a(1) = 1; for n > 1, a(n) is the smallest positive number such that a(n) - a(n-1) = sopfr(a(n)) + sopfr(a(n-1)), where sopfr(k) is the sum of the primes dividing k, with repetition.
15
1, 6, 20, 40, 106, 326, 568, 1294, 2071, 2323, 2603, 2867, 4467
OFFSET
1,2
COMMENTS
The sequence has only 12 terms beyond a(1) = 1 as there is no number k such that k - 4467 = sopfr(k) + sopfr(4467). See A369349 for the number of terms beyond each starting value n.
MAPLE
a(3) = 20 as a(2) = 6 and sopfr(20) + sopfr(6) = 9 + 5 = 14, which equals 20 - 6.
a(13) = 4467 as a(12) = 2867 and sopfr(4467) + sopfr(2867) = 1492 + 108 = 1600, which equals 4467 - 2867.
CROSSREFS
KEYWORD
nonn,fini,full
AUTHOR
Scott R. Shannon, Jan 21 2024
STATUS
approved