Mae' r ffwythiant FIB yn cyfrifo' r term N- fed o ddilyniant Fibonacci (1, 1, 2, 3, 5, 8, 13, 21...), lle mae pob rhif, ar ôl y ddau gyntaf, yn gyfanswm o' r ddau rif sy' n dod o' i flaen. Diffinir @ FIB( 0) i fod yn 0.
Function FIB calculates the Nth term of a Fibonacci sequence (1, 1, 2, 3, 5, 8, 13, 21...), in which each number, after the first two, is the sum of the two numbers immediately preceding it. FIB(0) is defined to be 0.