OFFSET
1,2
EXAMPLE
a(1) = 1 as 1 is the smallest number to have one number (k = 7) such that 7 - 1 = 6 = sopfr(7 + 1) = sopfr(8) = 6.
a(2) = 25 as 25 is the smallest number to have two numbers (k = 38, 41) such that 38 - 25 = 13 = sopfr(38 + 25) = sopfr(63) = 13, and 41 - 25 = 16 = sopfr(41 + 25) = sopfr(66) = 16.
a(3) = 55 as 55 is the smallest number to have three numbers (k = 70, 75, 83) such that 70 - 55 = 15 = sopfr(70 + 55) = sopfr(125) = 15, 75 - 55 = 20 = sopfr(75 + 55) = sopfr(130) = 20, and 83 - 55 = 28 = sopfr(83 + 55) = sopfr(138) = 28.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Scott R. Shannon, Feb 16 2024
STATUS
approved